Thanks for the replies, folks, however, it turns out that the pdf file was in fact corrupted, even though it opened fine! After having slogged through it page by page, I found several pages at what would've been about 77% through the document that were somehow merged over other pages, never seen that before?
In the end I've ended up deleting it, which is infuriating as it was the complete Phantom FG.1/FGR.2 RR Spey propulsion system AP101!
-RP