PDFtk - PDFtk is a simple tool for doing everyday things with PDF documents.
PDFelement Pro - PDFelement Pro is a feature-rich and highly useful solution that enables you to modify, populate, convert, sign and annotate PDFs.
Pdfinfo - Pdfinfo is a PDF document information and metadata extractor tool.
PDF Annotator - Comment and edit PDF. Add text, highlights, drawings, images. Insert, delete & merge pages. Handwritten PDF annotations. 2M+ downloads! FREE trial.
Edit PDF metadata - Edit PDF metadata is an online tool from PDFCandy that can manipulate PDF info and metadata.
DocMadeEasy - Edit and sign PDF. Send files safely and securely using end-to-end encryption with 256-bit AES. PDF document management and conversion.