“A TXE record is an “enriched text file” used to combine graphics with textual data for easier storage and retrieval of information stored in computer databases” doesn’t appear to be correct” — what is your source? The one you cited doesn’t match, it’s an advertisement for a “system scan”.
My understanding is that txe file is simply a text file with tags like html or rtf. Here’s the definition of “Enriched text” from the wikipedia —
http://en.wikipedia.org/wiki/Enriched_text?oldid=0
So, I think that X is just a blurry H.
The rest of your post is pure conjecture - for example there is no evidence that the PDF is based on “secondary sources” quite the contrary. The unevenness of the PDF we see is clearly the result of trying to create a readable version of a photostat of some kind - just look at the degree of compression and filtering they had to do.
Rgrds-Woody