I just found a manual for the game on the site where I usually find french manuals -I was inspired to look there by IAmSinistar mentioning in the release thread that this game's based on a BD (francophone comic) and linked to a page with the BD's french title, which allowed me to search for it in the database for the french manuals. I found it here and, despite what the page says, it is multilingual and has french,english,german inside. I'm not going to link to it in the gogmix though atm because all I saw there was install instructions and a story blurb which reduce its usefulness (ZFR will probably want the manual anyways though, since he counts story blurbs as more useful than I do...).
So I wanted to ask: Does the html manual include the same information as this manual I found or is it more extensive by any chance? Thanks in advance.

Thanks -no need to bother linking that other one then. It is a bit weird though that the html manual is more extensive than the one that (presumably) came in the box with the game - I suppose the html manual was given on the disc and thus was an early version of "The manual is on the disc" encountered in many modern games then...

Thanks again, updated the relevant gogmix entries. Because of the infamous character limit I had to delete the parts where I said where in the actual install folder are the manuals and that they can also be found online, but I guess that the start menu location will be more convenient for most people...

I got the following response today regarding adding missing manuals, particularly those from Appendix B. The original ticket was opened 22nd April.

"Hello, I apologise for the delayed response.
Our ability to release certain games and content is less dependable on the availability of the files, but more on the agreements with their publishers.
The bonuses are constantly being worked on, unfortunately I am unable to disclose any details.
I apologise for the inconvenience.

Regards,
Beta Ray Bill
GOG.com Support "

It might be possible that the pdf manual you linked was just a quickstart that came with a DVD case, while the boxed version had a more extensive one (the one on which the HTML one was based).

eBay shows the box version with a thickish manual, but it's hard to tell if it's same as the pdf version. I'll add this to the open questions, in case someone has it.

Could you do the same for the two Serious Sam games? They also have html manuals.

Also, you didn't answer my questions regarding the two discrepancies:

Thanks Judas. Any help from you is really appreciated. :)

Did you have anything to do with the fact that I finally got a response today? Seems a bit of a coincidence that I get an answer when you post to look into it.

Thank you, Judas. :)

The Deluxe Edition of Siege of Dragonspear, however is still missing the 4 artworks. :P (That's it from me, I won't bother you anymore today.)

Thank you again, Judas. :)

Jagged Alliance: Deadly Games is missing manual. And it's a bit shame, because the game uses keyboard a lot. For examle Z for zoom on item. Keyboard commands are not explained in the game at all.