What are some alternatives?
When comparing mergepdf.net and PDFill, you can also consider the following products
Merge PDF - Merge PDF is a user friendly PDF Reader.
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.
RoxyApps PDF Merge Tool - Merge multiple files of different formats in a single PDF file
PDFsam - PDFsam Basic, a free, open source, multi-platform software designed to split, merge, extract pages, mix and rotate PDF files
PDFMerge - PDF Split and Merge tool is implemented using the PdfSharp library and is either GUI or command...
PDF-XChange Editor - The smallest, fastest, most feature-rich PDF editor/viewer available