I find PDF Stream Dumper by David Zimmer and PDF CanOpener quite useful in PDF analysis.
A powerful text editor is also a must—and, 010 Editor has a binary template for the PDF format by Didier Stevens and Christian Mehlmauer which makes it a good option for reviewing PDF structures.
010 Editor — PDF Binary Template
Didier Stevens also has a few Python scripts that target PDF documents here:
2023 Update:
As of version 2.1.11, Forensic Email Intelligence has powerful PDF analysis capabilities, including the ability to review multiple metadata streams and extract timing information from PDF components, such as annotations. Details and video walkthrough:
2024 Update:
This shell script can also be useful for automating some examination tasks on PDFs:
I hope other examiners in the Community have some additional recommendations for you 