PDFTK Builder - PDFTK Builder is a free graphical interface to for PDFTK, making it much easier to use.
PDF Scissors - Crop pdf. Drop margin, whitespace. Auto crop all pages. Easy feature to make nice cropped pdf for ebook readers such as Amazon Kindle, Sony, Cybook etc.
PDFTools by SheelApps - PDFTools
Briss - Cross-platform application for cropping PDF files in a simple and fast way via a GUI.
QPDF - QPDF is a command-line program that does structural, content-preserving transformations on PDF...
PDF-XChange Editor - The smallest, fastest, most feature-rich PDF editor/viewer available