How to merge PDF files? When faced with this situation, many user initial thought is to use a PDF merging application to combine files. It’s great to attempt to keep things backup in these days and low document security. Document writing, conversion, sharing, and other required tasks (such as merging) can all be completed without using an Internet connection from the convenience of your desktop computer. Not only that, but you’ll be able to work with PDFs of different sizes, ranging from a few KB to a massive 150 MB document with 400 pages. Let’s have a look what are the reasons behind of merge PDF files.