CleverPDF is a comprehensive PDF web app, which offers 27 PDF tools online for free. It helps users convert PDF to Office, iWork, images and more. Users can also compress PDF, merge or split PDF, rotate PDF, add watermark or numbers to PDF and more. It's completely free, no sign-up is required.
PDF Joiner - This online tool allows you to join several PDF documents into a single file, free of charge.
Beyond Compare - Beyond Compare allows you to compare files and folders.
DocuPUB - DocuPUB is an online file converter, file merger, file compressor, and file resizing tool.
WinMerge - WinMerge is an open source differencing and merging tool for Windows.
PDFChef Merge PDF - PDFChef Merge PDF is an online tool that allows you to merge multiple PDf files into one quickly and securely.
Meld - What is Meld? Meld is a visual diff and merge tool targeted at developers.