litho

module

v0.0.1 Latest Latest Go to latest Published: Oct 29, 2026 License: AGPL-3.0

Details

Valid go.mod file
Redistributable license
Tagged version
Stable version
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Repository

github.com/gotenberg/litho

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Open Source Insights

README ¶

litho is a pure-Go PDF Conforming Processor. Read, validate, remediate, and produce PDF documents with no C dependencies.

litho implements ISO 32000 (PDF 1.4 through 2.0). It extracts text and structured content, validates against PDF/A, PDF/UA, WTPDF, Factur-X and ZUGFeRD, repairs non-conformant files, and edits, renders, encrypts and signs them. Every output is a valid PDF, and every public type honors its documented concurrency contract under -race.

Install

go get github.com/gotenberg/litho
go install github.com/gotenberg/litho/cmd/litho@latest

Go 1.27.3+. No CGO.

Prebuilt litho binaries for Linux (amd64, arm64, 386, armv7, ppc64le, riscv64, s390x, loong64), macOS, FreeBSD and Windows (amd64, arm64) ship with each GitHub release. On Linux, macOS and FreeBSD, the install script downloads one, verifies its checksum and installs it in /usr/local/bin:

curl -fsSL https://raw.githubusercontent.com/gotenberg/litho/main/install.sh | sh

Set LITHO_VERSION=v1.2.3 to pin a release and LITHO_INSTALL_DIR to install elsewhere.

Quick start

r, err := pdf.OpenFile(ctx, "input.pdf")
if err != nil {
	log.Fatal(err)
}
defer r.Close()

violations, err := r.ValidatePDFAReport(ctx, models.PDFA2b)

litho validate --profile PDF/A-2b document.pdf
litho remediate --profile PDF/A-2b --font-dir /usr/share/fonts -o fixed.pdf document.pdf
litho sign --cert cert.pem --key key.pem --reason Approved -o signed.pdf document.pdf

Run litho with no arguments to list every subcommand, or litho <command> -h to see its flags.

Features

Extract text with layout inference, positioned text, tables, images decoded to sRGB, annotations, form fields, bookmarks, attachments, and PDF 2.0 data (geospatial, measurements, 3D, formulas).
Validate PDF/A (every part and level), PDF/UA-1 and UA-2, WTPDF 1.0, Factur-X and ZUGFeRD, with the clause, test number and severity of each violation.
Remediate PDF/A, PDF/UA and WTPDF violations, embedding the fonts you supply, behind an integrity check that rolls back a fix that degrades the document.
Edit pages (rotate, delete, insert, split, merge), stamps and watermarks, metadata, form fields, bookmarks and attachments, auto-tagging, redaction, colour conversion and transparency flattening.
Render pages to images, on screen or for print, RGB or CMYK.
Protect with RC4, AES-128 or AES-256 encryption, and PKCS#7 or PAdES signatures up to B-LTA.
Optimize with object streams, stream deduplication, lossless image recompression and font subsetting.
Stay safe on hostile input: configurable resource limits, no panics, deterministic output.

Documentation

Library reference: Reader opens and extracts, Writer queues edits and writes, Pipeline chains them.
Examples: runnable programs for common tasks.
CLI reference: global flags, exit status, encrypted documents.

Contributing

Contributing guide: CONTRIBUTING.md
Bug reports: GitHub Issues
Security vulnerabilities: SECURITY.md

Acknowledgments

litho's text extraction, CMap handling and font resolution draw on Mozilla's PDF.js. Its PDF/A, PDF/UA and WTPDF rule set and clause numbering follow veraPDF.

Directories ¶

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Path	Synopsis
cmd
gen-adobe-ucs2 command Command gen-adobe-ucs2 generates the Adobe PDF-to-Unicode mapping resources that pkg/internal/typography/cmap supplies to the conformance checks.	Command gen-adobe-ucs2 generates the Adobe PDF-to-Unicode mapping resources that pkg/internal/typography/cmap supplies to the conformance checks.
gen-facturx-schematron command Command gen-facturx-schematron preprocesses the bundled Factur-X profile Schematron files by inlining external code-list lookups.	Command gen-facturx-schematron preprocesses the bundled Factur-X profile Schematron files by inlining external code-list lookups.
gen-iccv2 command Command gen-iccv2 generates the version 2 ICC profiles of pkg/internal/graphics/icc: the grey profile profiles/sgray-v2.icc and the CMYK printer profile profiles/cgats001-cmyk-v2.icc.	Command gen-iccv2 generates the version 2 ICC profiles of pkg/internal/graphics/icc: the grey profile profiles/sgray-v2.icc and the CMYK printer profile profiles/cgats001-cmyk-v2.icc.
gen-rules command Command gen-rules generates rules.go from VeraPDF validation profile XML files.	Command gen-rules generates rules.go from VeraPDF validation profile XML files.
gen-saslprep command Command gen-saslprep generates the stringprep tables of pkg/internal/crypto/saslprep from RFC 3454, Appendices A to D.	Command gen-saslprep generates the stringprep tables of pkg/internal/crypto/saslprep from RFC 3454, Appendices A to D.
gen-stdfonts command Command gen-stdfonts generates the PDF.js glyph tables of pkg/internal/typography/stdfonts from PDF.js's src/core/standard_fonts.js.	Command gen-stdfonts generates the PDF.js glyph tables of pkg/internal/typography/stdfonts from PDF.js's src/core/standard_fonts.js.
gen-verapdf-cmaps command Command gen-verapdf-cmaps generates the predefined encoding CMaps that pkg/internal/typography/cmap supplies to the conformance checks.	Command gen-verapdf-cmaps generates the predefined encoding CMaps that pkg/internal/typography/cmap supplies to the conformance checks.
litho command Command litho is the command-line front end to litho's public API in pkg/pdf.	Command litho is the command-line front end to litho's public API in pkg/pdf.
examples
compose command Command compose merges PDFs, then rotates the first page of the result and stamps every page with a DRAFT watermark, in one pipeline.	Command compose merges PDFs, then rotates the first page of the result and stamps every page with a DRAFT watermark, in one pipeline.
extract command Command extract prints the text of every page of a PDF and lists the images each page draws.	Command extract prints the text of every page of a PDF and lists the images each page draws.
remediate command Command remediate repairs a PDF for PDF/A-2b and writes the result.	Command remediate repairs a PDF for PDF/A-2b and writes the result.
render command Command render draws the first page of a PDF to a PNG image at 150 dpi.	Command render draws the first page of a PDF to a PNG image at 150 dpi.
sign command Command sign signs a PDF with a certificate and a private key read from PEM files, as a PAdES baseline signature appended in an incremental update.	Command sign signs a PDF with a certificate and a private key read from PEM files, as a PAdES baseline signature appended in an incremental update.
validate command Command validate checks a PDF against PDF/A-2b and prints each violation with its clause, test number and severity.	Command validate checks a PDF against PDF/A-2b and prints each violation with its clause, test number and severity.
internal
pkitest Package pkitest runs a public key infrastructure for tests: a root and an intermediate certificate authority, a signing certificate, an RFC 3161 timestamp authority, an RFC 6960 OCSP responder and the CRLs and certificates the certificates point at, all served by one local net/http/httptest server.	Package pkitest runs a public key infrastructure for tests: a root and an intermediate certificate authority, a signing certificate, an RFC 3161 timestamp authority, an RFC 6960 OCSP responder and the CRLs and certificates the certificates point at, all served by one local net/http/httptest server.
pkg
internal/annotation Package annotation extracts PDF annotation features: AcroForm fields, link and markup annotations, XFA form data, JavaScript calculation scripts, and measurement scales from annotation viewports.	Package annotation extracts PDF annotation features: AcroForm fields, link and markup annotations, XFA form data, JavaScript calculation scripts, and measurement scales from annotation viewports.
internal/bookmarks Package bookmarks auto-generates document outlines (bookmarks) from PDF content.	Package bookmarks auto-generates document outlines (bookmarks) from PDF content.
internal/compliance Package compliance validates PDFs against ISO 19005 (PDF/A), ISO 14289 (PDF/UA) and Well-Tagged PDF (WTPDF).	Package compliance validates PDFs against ISO 19005 (PDF/A), ISO 14289 (PDF/UA) and Well-Tagged PDF (WTPDF).
internal/compliance/cii_schemas Package cii_schemas bundles the UN/CEFACT Cross-Industry Invoice XSD set litho ships by default.	Package cii_schemas bundles the UN/CEFACT Cross-Industry Invoice XSD set litho ships by default.
internal/compliance/cii_schematron Package cii_schematron bundles the EN 16931 CII Schematron rule set litho ships by default.	Package cii_schematron bundles the EN 16931 CII Schematron rule set litho ships by default.
internal/core/ast Package ast defines the PDF object type system, including PdfNull, PdfBool, PdfInt, PdfReal, PdfName, PdfString, PdfArray, PdfDict, PdfStream, and PdfIndirectRef.	Package ast defines the PDF object type system, including PdfNull, PdfBool, PdfInt, PdfReal, PdfName, PdfString, PdfArray, PdfDict, PdfStream, and PdfIndirectRef.
internal/core/document Package document provides the high-level PDF document model.	Package document provides the high-level PDF document model.
internal/core/ioat Package ioat provides a buffered, stateful reader built on top of io.ReaderAt.	Package ioat provides a buffered, stateful reader built on top of io.ReaderAt.
internal/core/lexer Package lexer implements a byte-level tokenizer for the PDF file format, producing tokens for names, strings, hex strings, numbers, keywords, and delimiters.	Package lexer implements a byte-level tokenizer for the PDF file format, producing tokens for names, strings, hex strings, numbers, keywords, and delimiters.
internal/core/parser Package parser implements a recursive-descent parser that converts a PDF token stream into the AST object types defined in the ast package, handling dictionaries, arrays, indirect objects, indirect references, and the dictionaries of inline images.	Package parser implements a recursive-descent parser that converts a PDF token stream into the AST object types defined in the ast package, handling dictionaries, arrays, indirect objects, indirect references, and the dictionaries of inline images.
internal/core/writer Package writer provides the low-level primitives for emitting valid PDF byte sequences: object serialization, cross-reference table/stream writing, and object number allocation.	Package writer provides the low-level primitives for emitting valid PDF byte sequences: object serialization, cross-reference table/stream writing, and object number allocation.
internal/core/xref Package xref parses PDF cross-reference tables and cross-reference streams, building an index that maps object numbers to their byte offsets or object stream locations.	Package xref parses PDF cross-reference tables and cross-reference streams, building an index that maps object numbers to their byte offsets or object stream locations.
internal/crypto Package crypto implements PDF standard security handlers (V1 through V5), supporting RC4, AES-128, and AES-256 encryption with owner and user password authentication.	Package crypto implements PDF standard security handlers (V1 through V5), supporting RC4, AES-128, and AES-256 encryption with owner and user password authentication.
internal/crypto/saslprep Package saslprep implements SASLprep (RFC 4013), the stringprep (RFC 3454) profile ISO 32000-2, 7.6.4.3.3 applies to an AES-256 password before the password is encoded as UTF-8 and truncated to 127 bytes.	Package saslprep implements SASLprep (RFC 4013), the stringprep (RFC 3454) profile ISO 32000-2, 7.6.4.3.3 applies to an AES-256 password before the password is encoded as UTF-8 and truncated to 127 bytes.
internal/filter Package filter decodes and encodes PDF stream filters, including FlateDecode, LZWDecode, ASCII85Decode, ASCIIHexDecode, and PNG/TIFF predictor processing.	Package filter decodes and encodes PDF stream filters, including FlateDecode, LZWDecode, ASCII85Decode, ASCIIHexDecode, and PNG/TIFF predictor processing.
internal/filter/ccitt Package ccitt decodes the CCITT facsimile data of a CCITTFaxDecode stream (ISO 32000-1, 7.4.6): Group 3 one-dimensional and mixed coding (ITU-T T.4) and Group 4 two-dimensional coding (ITU-T T.6), under the parameters of ISO 32000-1, Table 11.	Package ccitt decodes the CCITT facsimile data of a CCITTFaxDecode stream (ISO 32000-1, 7.4.6): Group 3 one-dimensional and mixed coding (ITU-T T.4) and Group 4 two-dimensional coding (ITU-T T.6), under the parameters of ISO 32000-1, Table 11.
internal/filter/dct Package dct decodes the JPEG data of a DCTDecode stream (ISO 32000-1, 7.4.8): baseline and progressive Huffman-coded frames of ITU-T T.81, with the colour transforms of Adobe Technical Note #5116 that ISO 32000-1 defers to.	Package dct decodes the JPEG data of a DCTDecode stream (ISO 32000-1, 7.4.8): baseline and progressive Huffman-coded frames of ITU-T T.81, with the colour transforms of Adobe Technical Note #5116 that ISO 32000-1 defers to.
internal/filter/jbig2 Package jbig2 decodes JBIG2 bi-level image data (ITU-T T.88 \| ISO/IEC 14492) in the embedded organisation that ISO 32000-1, 7.4.7 requires of a JBIG2Decode stream: the segments of one page, optionally preceded by global segments held in a separate stream.	Package jbig2 decodes JBIG2 bi-level image data (ITU-T T.88 \| ISO/IEC 14492) in the embedded organisation that ISO 32000-1, 7.4.7 requires of a JBIG2Decode stream: the segments of one page, optionally preceded by global segments held in a separate stream.
internal/filter/jpx Package jpx decodes JPEG 2000 image data (ITU-T T.800 \| ISO/IEC 15444-1) as ISO 32000-1, 7.4.9 requires of a JPXDecode stream: a JP2 file whose first codestream holds the image.	Package jpx decodes JPEG 2000 image data (ITU-T T.800 \| ISO/IEC 15444-1) as ISO 32000-1, 7.4.9 requires of a JPXDecode stream: a JP2 file whose first codestream holds the image.
internal/filter/mq Package mq implements the MQ adaptive binary arithmetic decoder defined by ITU-T T.88, Annex E. Each call to Decoder.Decode returns one binary decision and adapts the probability state of the Context it was coded in.	Package mq implements the MQ adaptive binary arithmetic decoder defined by ITU-T T.88, Annex E. Each call to Decoder.Decode returns one binary decision and adapts the probability state of the Context it was coded in.
internal/flatten Package flatten removes live transparency from page content: it composites each region where transparent content paints into one opaque image, and keeps everything outside those regions, and every glyph inside them, as vector content.	Package flatten removes live transparency from page content: it composites each region where transparent content paints into one opaque image, and keeps everything outside those regions, and every glyph inside them, as vector content.