[DaltonST]

You suggestion to attach the images to the OP and not make them available within the PI itself is not scalable at all to larger and more complex PIs that have large instruction manuals. My upcoming PI has dozens of images embedded within text, and they form a cohesive whole. Uploading them per your suggestion and expecting the users to download all of them, and then rearrange them in logical sequence, and then read them in the exact sequence they are intended to be read in, would be wishful thinking, and also quite abusive to the users themselves.

You opinion "I doubt anyone needs to view the PI help outside of Calibre" implicitly contradicts your first post that "PDF is a horrible format which invariably invokes laggy viewers". The instructions require the new users of the PI to Restart Calibre two (2) times, because there is a Custom Column involved. If the instructions were not a sub-process of the operating system, they would be closed when Calibre restarted. The user would suffer "lagginess" unnecessarily because the instructions would have to be reopened ("with lagginess") after Calibre restarted. That is not true for using an external viewer that is independent of Calibre, and remains open while Calibre restarts.

You opinion "I doubt anyone needs to view the PI help outside of Calibre" also is flatly incorrect when it comes to more complex PIs that involve the use of other PC tools (such as MS Excel or OpenOffice Calc or Google Docs) simultaneously with the perusal of the instructions. Calibre may not even be running for long periods of time when they need to perform PI-related tasks outside of Calibre.

In short, your comments and suggestions are either (a) not scalable to more complex PIs with more complex instructions; or (b) impractical; or (c) abusive to the users.

Again, my decisions about the instructions were not at all arbitrary or capricious or based on speculation or "doubts". The root criterion that forced the .pdf instruction file format is the Forum Rule about multiple zip files in the Original Post.

If the Forum Admins ever change that Rule, I will then convert all of my MS Word instructions into HTML rather than Adobe's Portable Document Format.

Regardless of the format, the viewer will be an external sub-process to Calibre for the reasons cited above. It might even be Calibre's ebook Viewer itself, which of course is an external sub-process to Calibre, and remains open when Calibre closes, as it should.