PDFtk is a simple tool for doing everyday things with PDF documents. Developed by Angus Johnson - GNU General Public License
License: Open Source
PDFsam is a user-friendly tool ideal for basic PDF manipulations like merging and splitting without needing technical skills, while PDFTK Builder caters to advanced users with its powerful command-line interface and extensive features for PDF management. Both are free and cross-platform, but PDFTK Builder offers more advanced functionalities at the expense of ease of use.