diff-pdf is a tool for visually comparing two PDFs. The source code is here.
Ranked in these QuestionsQuestion Ranking
Pro GPL license
Could be adopted and improved by anyone.
Pro Supports multiple pages well
Shows all pages in the sidebar, lets you compare them all.
Pro Whole-page preview in side panel
If pages from the two documents match, they are shown in green on the left side panel, so you can save time focusing only on the pages that don't match.
Pro Graphical red/blue diff
Black lines in the original files are shown as red/blue lines, which become black when they are identical.
Con Crashes often
Trying to offset one page vs the other causes a crash, etc.
Con Offset is very slow
If two pages are offset by a large amount, it will take forever to move them one pixel at a time, since each pixel takes a long time to reload.
The main Git page says"this repository is provided as-is and the code is not being actively developed.".