litho

Pure-Go PDF Conforming Processor for 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, with no C dependencies.

Note

litho powers the PDF operations of Gotenberg 9. Its API is pre-1.0 and may change between releases.

Install

go get github.com/gotenberg/litho

Go 1.27.3+. No CGO.

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)

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, to one profile or to a PDF/A and PDF/UA pair at once, 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.

Contributing

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

License

litho is licensed under the GNU Affero General Public License v3.0.

Gotenberg embeds litho and ships it under the MIT License, as its copyright owner allows. Contributors sign the Contributor License Agreement, which grants that right for their contributions. Any other use of litho follows the AGPL-3.0.

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.