PDFtodo!

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.

The smallest, fastest, most feature-rich PDF editor/viewer available

CloudConvert is a online file conversion tool. more than 200 different audio, video, document, ebook, archive, image, spreadsheet and presentation formats supported.

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 .

Master PDF Editor is complete solution for editing PDF and XPS files. You can insert, edit, remove, copy, add images or graphics. Export, import, remove and change page layouts. Also Master PDF Editor provides full functionality for changing PDF information, including author, title, subject, keywords, creator, and producer information.

Nitro Pro gives you everything you need to create, convert, edit, sign, and share 100% industry-standard PDF files. It's simple, straightforward, and intuitive to use — so you can work more productively, your way.

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.

PDF Chain is a GUI for pdftk written with gtkmm. You can merge some pdf files to one pdf file or split, set background/stamp or add attachments to one pdf file. There are also some options and tools.

Free conversion online of many type of documents (images, text, video, audio...), and download from video platforms (youtube etc.).

Free (and open source) editor for manipulating PDF documents. GUI version + commandline interface. Scripting is used to a great extent in editor and almost anything can be scripted, it is possible to create own scripts or plugins.