In 2003 the PTO started and provided patent file histories on the PAIR electronic Image File Wrapper site. However the Non-Patent Lit (NPL) documents are not available due to copyright issues.
Also the older patent file wrappers/histories are not yet available on the PAIR system.
NPL and older patent file histories can be obtained from vendors such as ...
As a self-appointed Unix guru ;-) 😉 and in accordance with StackExchange's roots, I ended up using command-line tools like "pdftk" and "perl" to solve this problem.
On an Apple Mac:
install "pdftk" command-line tool (directly or via MacPorts)
copy this script into a text file and run it with a path to the Image File Wrapper PDF as argument.