Smallpdf - PDF document management and conversion suite
Beyond Compare - Beyond Compare allows you to compare files and folders.
iLovePDF - Free online PDF tool set
WinMerge - WinMerge is an open source differencing and merging tool for Windows.
Adobe Acrobat DC - Make your job easier with Adobe Acrobat DC, the trusted PDF creator. Use Acrobat to convert, edit and sign PDF files at your desk or on the go.
Meld - What is Meld? Meld is a visual diff and merge tool targeted at developers.