MSWord can split tables anywhere. If all of the beliefs were in a single table and the type of belief were in a column with sideways text spanning all the appropriate rows, it might fit on just two pages instead of three.
I'm well aware of splitting tables and used it extensively in the document. If a table split ran to 2 pages plus a small amount of lines on a third page, I adjusted the splits to a more equal size so that enough of a table was visible on a page to make comparisons within a page better, instead of leaving something like 1-3 lines left over on a new page.
Most of the tables were carefully fitted to maintain a consistent look while keeping row heights as small as practical so more rows fit on a page. Adding columns will drive row heights higher resulting in fewer rows per page and a reduction in comparability, as well as a larger page count.
My list of spy locations above is complete based on your PDF (even if I included an "etc" above). But it is possible to train more spies than just 2 or 3 so there must be some other places that grant spies. Last night when I ran the game I forgot to look up the additional spots in the tech graph.
I know all the adjacency bonus are elsewhere in the file. My first sentence was "some duplication would be helpful". I missed your note that appendixes were planned. As for size you could always split in half: Civilization Reference Vol 1 Beliefs thru Improvements and Civilization Reference Vol 2 Leaders thru Wonders. PDF format supports cross-PDF linking. Not sure you can do it in MSWord though.
Lots of stuff I'd like to add beyond a cross reference, stuff like breakdown tables of military units by era and by type in addition to alphabetical. That would allow seeing what you had and were up against in a particular era or see the progress of power in a particular units class.
Splitting into multiple documents is fully supported in MSWord, but it doesn't really buy you anything. The issue is total bytes transferred in hosting and it's cost for CivFanatics. Dling two sections that add up to the same amount of bytes doesn't gain you anything in hosting total bytes delivered.
The MSWord doc source is 113 Mb+. The primary culprit is the graphics. Most of the icons I got from screen capture came off the screen at 258x253 pixels (the big upper right icons in a double frame with cut corners you see in the civilopedia). That's 261,096 bytes (258*253 pixels * 4 bytes (RGB+Alpha) per each occurrence in the document. That includes the tiny icons next to stuff like techs and civics links in rows. They are just shrunken in display size, not in pixel count. The full set of 722 graphics used is 32,982,784 bytes for just one occurrence of each image. The images are embedded in the document many times. While I could shrink the document a lot by linking the images to a file directory instead of embedding, then I'd have to deliver the whole image set to go with the document. Even RARed down it's 25Mb+.
I'm hoping we'll soon see either the release of the toolset (possibly giving us multiple icon sizes to choose from) or some graphic artist with the feel for shrinking pixel size down, while still fooling the eye for apparent detail will make a set. I'm not such a graphic artist with thousands of hours of hands on time to get the 'feel' for using varied color tones as single pixels to fool the eye with detail in a small image.
While I could easily reduce the images to any pixel size desired, it would result in massive lost detail. Look at how detailed the unit images are in civilopedia. Take the Biplane for example. The connecting lines between the wings are only 1-2 pixels wide, shrink that to say 64x64 and the results wouldn't be pretty. Or look at the Tank. I choose to keep the quality despite the size penalty.
Fortunately, passing the DOC into LibreOffice and exporting to PDF resulted in a large decrease in size. I suspect this a result of duplicate images being recognized and storing only one copy. Give me a good quality set of smaller images, and I've have the slack to add lots of things and probably still be smaller than it is now.