Which one is the latest version?
What are the differences with version A and version B?
The lists go on and you feel like you want to bite your finger nail now......
Luckily, there is a free software, Diffpdf (Windows version) that can be easily used to compare your document side by side.
No instruction is needed to use this software. It pretty straight forward.
Arch Linux/Manjaro Version
diffpdf is available in the AUR. Installation is straight forward using command:
yaourt -S diffpdf
Other than methods described above, linux user can also try method explained here.
pdftotext file1.pdf pdftotext file2.pdf kdiff3 file1.txt file2.txt