Though Adobe Acrobat is a great software for viewing PDF files, the free Reader version doesn't provide much functionalities when it comes to editing or converting the file itself. For example, adding or updating the table of contents, a feature that I find myself frequently needing, can't be done within the free version. Before going on to spend money again, I found some nice open source software alternatives that can help me do the basic stuff I wanted.
- Ghostscript is an interpreter for PostScript and PDF files. It can mainly be used for converting between the two file types.
- Pandoc is a universal document converter that can convert to PDF from markdown, LaTeX, etc.
- jPDF Tweak
- jPDF Tweak can be used for most basic functions (e.g. combine, split, rotate, reorder, watermark, encrypt, sign, bookmark, metadata, etc.). It's a Java Swing application and so will need a Java runtime installed.
- jPDFBookmarks is solely for creating or editing bookmarks within PDF files. Almost as what Adobe Acrobat Pro does, the software lets bookmarks be positioned anywhere and can be displayed with various styles. Development seems to have halted since 2012, but the program still runs great. You'll also need a Java runtime in order to run this Java application.