PDF editing tools introduced under Ubuntu

The following description for the Ubuntu users several useful PDF editing tools.
Pdftk:
If the PDF is an electronic paper, Pdftk applicator is a stamp, punch, glue, developer,and an X-ray glass. Pdftk is a simple PDF-purpose tool, use it, you can:
Merge PDF documents

Split PDF
Rotate PDF pages
PDF password decryption
Encrypted PDF
XFDF with FDF Data or to fill in PDF form
Add a watermark or tag
Show PDF Information
Modify PDF Information
Attach files to PDF pages or PDF documents
Extract PDF attachments
Decomposition of the form of PDF documents into a single page
PDF compression decompression and re-flow
Repair damaged PDF documents
PDF allows you to easily manage your PDF documents and is free of charge, can beWindows, Linux MACOSX, FreeBSD and Solaris.   

Ahead PDF passord remover:
With this tool, you can easily remove pdf password from your pdf files.

Ahead PDF encrypt:
With this tool, you can easily encrypt your pdf files with user or owner password.

Pdfedit:
PDFedit allows you to edit the PDF document. You can change any part of the PDF.You can use scripts to add functionality.
Scripts can use other external editor, and can customize their own scripts.