PDFMerge!

PDFsam Basic is a free, open source, multi-platform software designed to:

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.

PDFTK Builder is a free graphical interface to for PDFTK, making it much easier to use. It is a easy to use tool to collate (merge), split, encrypt, decrypt, stamp and rotate (only 90°, 180° or 270°) pdf documents. Portable Version: http://portableapps.com/apps/office/pdftk_builder_portable .

PDF-Shuffler is a small python-gtk application, which helps the user to merge or split pdf documents and rotate, crop and rearrange their pages using an interactive and intuitive graphical interface. It is a frontend for python-pyPdf.

With PDFill you can create, fill, delete and submit PDF form fields; insert new formatted text, check, image, hyperlink, whiteout, highlight, drawing, comment and annotation anywhere in the document; save, print or email the filled and password-protected PDF; save and resume your filling anytime. PDF Writer is Freeware. PDF Editor is not.

You can reorder, rotate, and remove pages, export images from a document, edit the title, subject, author, and keywords, and combine documents via drag and drop.

UnityPDF lets you merge, split, divide, rotate, protect PDF files and more. All features are easy to use and do not require complex skills.

Create your PDF files like a Pro

Functions: Split pdf-files, Merge pdf-files together, Compose new PDF-Files while using individual sorting, customized patterns (similar to Word printing), etc. You can even append encrypted PDF files to another PDF document Faster than Java based PDF Split & Merge Tools Can be used on USB-Sticks as PortableApp PDF Split & Merge Tool Support for English and German is included.

PyPDF2 - A utility to read and write pdfs with Python

Convert all the mainstream formats to PDF, merge them with other PDF formats or convert PDF files to other formats as well.

PDFMate Free PDF Merger is an easy-to-use but powerful 5-in-1 PDF application, combining functions of PDF Merger, Image & PDF Joiner, PDF Breaker, JPG to PDF Converter, and PDF Encrypter.