Open-Source Acrobat Alternatives by PDF Task

Open-source PDF task checklist

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• 1. Write down one job before you install anything: change text that is already in the PDF, combine files, separate pages, sign, fill or create a form, make a scan searchable, or make a file smaller. Also write down whether the file can leave the computer. The pages below do not describe the same control. A Windows merge without Acrobat, a Mac Preview combine, Preview’s text limit, and a Mac or iPhone signature stay on their own guides.
• 2. For Stirling PDF, keep the homepage, the LICENSE file, the desktop page, and the server plans page apart. The documentation homepage says Stirling is a private, open-source PDF editor and processor, and that you can read, edit, and automate PDFs in a browser, on your own computer, or on your own servers. The desktop card says to install the editor on Windows, Mac, and Linux, and that it works offline. The desktop page’s table lists Windows 10 or 11 (x64), Windows on ARM, macOS 10.15 or later (Apple silicon and Intel), and Linux (x86_64). It says the desktop app runs the editor and most tools on your own computer, with no account needed, and that tools that cannot run locally need Stirling Cloud or your organisation’s server. The LICENSE file on the main branch, copyright 2025 Stirling PDF Inc., says content outside the named directories is available under the MIT License. The named directories are app/proprietary/, app/saas/, engine/, frontend/src/editor/proprietary/, frontend/src/editor/desktop/, frontend/src/editor/saas/, frontend/src/editor/cloud/, and frontend/src/processor/, each under the license file in that directory if the directory exists. The plans page says a self-hosted server runs on the Free plan until you add Team or Enterprise, that Free is 5 users, and that prices are on stirling.com/pricing. That plans page does not display a dollar amount. Its Free column says yes for all PDF tools, the REST API, OAuth2 / OIDC single sign-on, and server certificate signing.

  Stirling PDF LICENSE: MIT outside the named directories · official help checked 2026-11-02

• 3. For what Stirling names as a PDF tool, use the functionality page, and keep the file-location sentences on the pages that print them. The functionality page says not every tool is available everywhere, and that in the desktop app tools with a cloud badge need Stirling Cloud or a server. It names PDF Text Editor as edit the existing text and images in a PDF. It names Merge as combine several PDFs into one, Split as split one PDF into several files, and Compress as make a PDF smaller. It names OCR / Cleanup scans as make scanned PDFs searchable and clean them up. It names Sign as add a drawn, typed, or image signature, and Sign with Certificate as add a digital signature that proves who signed and shows later changes. It names Form Editor as fill in, add, and edit form fields, and Auto Form Detection as find form fields and make a PDF fillable. Add Text, on the same page, is type text anywhere on a page. That is not the PDF Text Editor sentence. The “Where your tools run” page says that in Local Only every tool runs on your computer and nothing is uploaded, and that tools the built-in engine cannot run show a cloud badge and ask you to sign in to Stirling Cloud or connect to a server. Its list of tools that usually need Cloud or a server begins with OCR, and it includes the Convert images to line art option in Compress. The FAQ’s Stirling Cloud bullet says tools such as compress, OCR, and convert send the file to Stirling’s servers and return the result. Its desktop bullet says that in Local Only mode nothing leaves your computer, and a tool that cannot run locally is blocked, not uploaded. Those two location pages are not the functionality page’s tool names.

  Stirling PDF: PDF Text Editor, Merge, Split, Sign, forms, OCR, and Compress · official help checked 2026-11-02

• 4. For LibreOffice, keep the homepage, the licenses page, and the system requirements page apart from the PDF help. On 2 November 2026 the homepage printed “LibreOffice 26.8 is here!” and “LibreOffice is an open source office suite.” It says the tools are available at no cost to you, and that it is free and open source software. The Draw card on that page says “Design everything from simple diagrams to complex 3D illustrations.” That card does not say PDF. The licenses page says LibreOffice is Free Software and is made available under the Mozilla Public License v2.0, and that contributions are asked for under both the Mozilla Public License v2 and the GNU Lesser GPL v3+ licenses. The system requirements page lists Windows 10 or 11, with LibreOffice fully supported on Windows 11, macOS 11 or newer, and Linux kernel version 4.18 or higher. The Android/Linux line says to see LibreOffice Viewer for Android. These three pages do not name Merge, Split, OCR, or a PDF text editor.

  LibreOffice licenses: Free Software under the Mozilla Public License v2.0 · official help checked 2026-11-02

• 5. For a PDF job in LibreOffice, keep each help page’s sentence on that page. The filter table’s PDFIMPORT section lists “PDF - Portable Document Format (Draw)” with the API name draw_pdf_import, and it also lists Impress and Writer PDF import filters. The table does not describe a click path and does not say OCR. Consolidate Text says to choose Shape - Consolidate Text when two or more text boxes are selected, that consolidation joins text boxes and enables text reflow, and that the command is especially useful for editing PDF documents with LibreOffice Draw. It says you must manually fix paragraphing and set paragraph properties after consolidation, and that the previous text box objects are deleted. The PDF export General tab is File - Export As - Export as PDF - General tab. Its Pages box exports the pages you type, with examples such as 3-6 and 7;9;11. JPEG compression says that with a low quality level some pixels are lost and file sizes are reduced. Create PDF form says to choose to create a PDF form that can be filled out and printed by the user of the PDF document. Hybrid PDF says the exported file remains fully editable in LibreOffice. That hybrid sentence is about the file you export. It is not the import-filter row. Sign Existing PDF says LibreOffice can digitally sign an existing PDF, and that the PDF document opens in LibreOffice Draw in read only mode. The Digital Signatures export tab says the signed PDF export uses the keys and X.509 certificates already stored in your default key store location or on a smartcard. The help page’s Mac switch prints LibreOffice - Preferences, and the default switch prints Tools - Options, then both continue to LibreOffice - Security - Certificate Path. The Draw Page menu’s “Insert Slide Page/Objects from File” says it allows you to insert the entire file or specific elements in the file. That menu page does not use the word PDF. None of these LibreOffice pages print the word OCR.

  LibreOffice Draw: Consolidate Text for editing PDF documents · official help checked 2026-11-02

• 6. For Okular, keep the homepage, the download page, and the handbook pages apart. The homepage says Okular is multi-platform and lets you read PDF documents, and that it is released under the GPLv2+ and is fully Free Software. It says you can add inline and popup notes, highlight and underline text, or add your own text. It says you can view and verify digital signatures in PDFs and sign PDFs yourself. The news line prints “Okular 26.08 released” and “Thursday, 16 April 2026.” The download page says Linux packages can be installed from Discover, GNOME Software, or the distribution’s software store, and that a Flatpak is on Flathub. It says the Microsoft Store is the recommended place to install Okular and that the version there has been tested by the developers. It then says untested nightly builds are offered for Windows, macOS (ARM), and macOS (Intel). The forms page says that if the current document has forms, click Show Forms or choose View → Show Forms to enter data into the form fields. It does not say to create a new field. The annotations page says Typewriter adds text on a transparent background and is useful for filling out forms lacking integrated editable text fields. It says annotations can be saved into the PDF with File → Save or File → Save As. It does not say Typewriter replaces a sentence that is already in the file. Its stamp note says the feature is experimental and that custom stamps inserted in PDF documents are not visible in PDF readers other than Okular. The signatures page says Okular does not have the ability to create such certificates, and that adding signatures needs at least Poppler 21.01. The Tools menu says Digitally Sign... starts the digital signature creation workflow, and that addition of digital signatures is only supported for PDF files at this point. The Okular pages checked do not list Merge, Split, OCR, or Compress.

  Okular: GPLv2+, annotations, forms, and PDF signatures · official help checked 2026-11-02

• 7. After any change you make yourself, reopen the saved file and check the one job you wrote down. This guide did not save a file, so it does not report a page count, a recognized word, or a smaller file size. Stirling’s functionality names and LibreOffice’s export sentences are not that check. Okular’s Typewriter sentence is not an existing-text edit. The edition records linked below are the catalog pages. They are not a new test.

  Check the file you save; this guide did not open one · official help checked 2026-11-02