Yes, I am sure that the E-series manuals were on HP's website. They were never at docs.hp.com but rather at the customer care site. At the top of this forum is a sticky thread with HP links. Read it. I'm not as positive about the I-class since I never looked for those specificly.
But there were operators and installation manuals available, not service manuals (which is what I wanted at the time). Only a few primitive indicator lights are on these boxes and they are obvious. The main indicator is a four character display. With an OS running, it will have FxyF. This display is under the control of firmware and when the OS runs, it instructs the firmware as to what to display. So all of the models are the same and that is why you should read the manuals I linked. I worked on E-class boxes for several years but I never read an E-class specific manual. These early models do not have hardware logs. Any logs are maintained by the OS and documented in the OS manuals.
And look at the dates on those HP journal articles annoucing these products and compare them to this
PDF timeline. Even if PDF had been invented recently, there are scanners that can convert printed pages to PDF and other formats. HP might have access to one considering that they manufacture scanners. Lots of older material is available in PDF format.