Best open-source alternatives to Adobe Acrobat

Stirling PDF is a PDF editing platform aimed at individuals and organizations that need to manipulate documents locally or on their own infrastructure. It provides a browser-based interface, a desktop client, and a self-hosted server option, allowing users to work with PDFs without sending documents to external services. The project emphasizes broad PDF handling capabilities, including editing, signing, redaction, conversion, OCR, compression, and automation. It also positions itself as a developer-friendly platform with REST APIs for integration, no-code workflows, and enterprise-oriented features such as SSO and auditing. The documentation site and paid enterprise offerings are referenced for more complete installation and feature details.

Gotenberg is a Docker-based document conversion service designed to turn many kinds of input into PDF files through a simple HTTP API. It is aimed at developers and teams that need reliable, self-hosted PDF generation without having to manage browser, office, or font dependencies themselves. The project supports conversion from HTML, URLs, Markdown, and office document formats, and it also provides PDF manipulation features such as merging, splitting, rotating, flattening, watermarking, stamping, and encryption. It additionally offers screenshot generation and support for PDF/A and PDF/UA compliance, making it useful for automation pipelines and production document workflows.

OpenSign is an open source document e-signing platform positioned as an alternative to DocuSign and other commercial signing services. It is designed for teams and individuals who need to send, sign, annotate, and manage PDF documents in a self-hosted or cloud-hosted environment. The project includes core signing workflows such as inviting multiple signers, signing in sequence, using templates, and managing documents in a centralized drive. It also adds security and compliance-oriented features like guest signer OTP verification, audit trails, completion certificates, and customizable email notifications. The README also highlights an API and third-party integrations, making it suitable for organizations that want to embed signing into existing systems.

Documenso is an open-source document-signing platform intended as a self-hostable alternative to DocuSign. The README emphasizes trust, transparency, and control, encouraging users to run the software themselves and review how it works under the hood. It is aimed at teams and organizations that want digital signing infrastructure they can own and operate. The project is built with TypeScript, React Router, Prisma, Tailwind, shadcn/ui, tRPC, and related PDF tooling. It can be run locally for development with Node.js and PostgreSQL, or deployed via Docker containers pulled from DockerHub or GitHub Container Registry. The README also points to an Enterprise plan for large organizations, suggesting additional flexibility and control beyond the self-hosted version.

DocuSeal is an open source document signing and form-filling platform aimed at teams and businesses that need to create, distribute, and process PDF-based workflows. It provides a web interface for building fillable PDF forms, collecting responses, and managing signatures on any device with a mobile-optimized experience. The project can be self-hosted and deployed through Docker or Docker Compose, with examples for running it on a private server and under a custom domain. It supports common storage backends, email delivery via SMTP, and an API/webhooks model for integration into other applications. The README also notes enterprise-style capabilities such as user management and pro features like SSO/SAML, reminders, bulk sending, and embedded signing components.

Signature PDF is a web application for working with PDF files in a browser. It targets users who need to sign documents, reorganize pages, edit metadata, and compress files without relying on a desktop PDF editor. The project supports collaborative signing, including a multi-signature mode where multiple people can sign the same PDF. It also includes options for storing uploaded PDFs on the server, encrypting those stored files, customizing retention periods, and defining default metadata fields. Installation is documented for Debian/Ubuntu, Docker, Alpine Linux, and package-based deployment, and the README lists several public instances where the software can be used directly.

Papermerge DMS is an open source document management system built for scanned documents and digital archives. It is aimed at users who need to store, organize, and search paper scans or image-based documents over the long term, while providing a desktop-like browsing experience in a web application. The project supports document ingestion, OCR-based text extraction, indexing, tagging, hierarchical folders, document versioning, and full-text search. It also includes a REST API, multi-user capabilities, group ownership, and document sharing between users or groups. The README shows Docker-based startup instructions as well as source-based development and testing workflows for both backend and frontend components.

BentoPDF is a client-side PDF toolkit designed for people who want to manipulate PDFs without uploading files to a server. It is positioned as privacy-first and self-hostable, making it suitable for users and organizations that need local processing and control over their documents. The project emphasizes browser-based workflows rather than backend processing.