DA File Access versun Non-DA

I am a long-time QuickPDF user (via Delphi 7).  I understand the basic concept of the DA function calls (not loading an entire document into memory has very significant performance benefits for things like single page rendering).  What I am having a hard time understanding is the programming logic of having what are essentially two totally separate libraries in a single object.  It is dangerously easy to mix DA and Non-DA function calls, and the result is not "fatal", just "odd".  The only discussion of "DA" I can find is a paragraph in the online docs along with a list of DA functions.

It seems obvious (to me) that there should be, at least, a global boolean variable/property of something like DALibraryMode, which other functions can use to make the correct calls to perform similar pdf functions without having to know or care which way the file was opened.

It would be very helpful to provide some underlying logic as to what functions (or function groups) are included and which are not.  I am also discovering that the calls of things like "SetPageBox" and "DASetPageBox" are merely similar, not identical.  Just for comparisun, the two "GetPageBox" functions use identical calling sequences.  (I think that writing this paragraph has just solved one of the things that has been bugging me for the last couple of days - I assumed they were both identical)

I THINK I am discovering that the DA functions do not honor or recognize things like "Origin" and "MeasurementUnits", but without an underlying philosophy of DA versus Non-DA, it is just trial-and-error to figure this out.

Thanks - Howard

OK...  I can't find any reference to "Quick PDF" on the Foxit website forum area.  In past years, this forum was an appropriate place to discuss Quick PDF from a user's perspective.  In my mind, as a user, I can't "use" something unless I have a good gut feeling for what it is doing under the hood.  I am not necessarily reporting a bug in the software, but a lack of clarity in the documentation to help me predict what each of the thousand++ function calls are supposed to do.  The reference manual helps a great deal, but it ONLY describes syntax, not purpose or limitations.

For example - the minimal discussion of "DA" says to let them know if additional functions need to be added to the DA part of the library.  Can you give me a link to the part of the Foxit website where I would make such a suggestion?  Thanks - Howard