(I used it just once)

Neevia PDFtoolbox is a powerful set of tools combined into one installer. This, without having any Adobe software, enables anyone with a need to manipulate PDF files to easily stamp, split, merge, compress, digitally sign, encrypt and resize PDF documents.

If you are a developer PDFtoolbox contains practically everything you need to create a robust solution that provides a wide range of features for manipulating PDF files.


Key features:

Merge, split PDF documents;
Resize PDF files (custom page size support);
Encrypt, decrypt (password required) PDF files;
Stamp PDF documents with custom watermarks;
Digitally sign, time stamp PDF files;
Compress, optimize PDF files;
Fully multi-threaded;
Does NOT require any Adobe products;
 
http://www.neeviapdf.com/PDFtoolbox/