Another team in my library is digitising one of our older theses but had a problem with a couple of pages so asked me to scan those pages from our deposit copy. Unfortunately we had the same problem - the glue used 50 years ago to glue photographs into the thesis has lost any and all adhesive properties it once had.
The problem was exacerbated by the fact that the pages in question were of several photos of oscillographs - and I had no idea either where each one went or which way up it went.
Fortunately someone in the other team had the bright idea of matching the back of the photo to the indentation in the page. I had another look at our copy - there was no indentation, but the old glue left a browning stain so the back each photo had an individual pattern (finger prints, brush strokes, dappling, or at least different shaped corners) which was the mirror image of that on the page.
And then I used an OHT transparency to hold the photos in place while I scanned them (since I don't want to use any glue before talking to our conservation people). Mission accomplished!