Honestly, when I'm hunting down a PDF of 'Allegiant' I expect a little variety — publishers and file creators love to mess with page counts. The easy practical answer is: most official editions of 'Allegiant' by Veronica Roth are around 525–526 pages in their U.S. paperback/hardcover prints, so a nicely formatted PDF will usually land in that ballpark.
That said, PDFs can behave wildly: a publisher-created PDF that mirrors the physical book will show those 525–526 pages, but a scanned copy (one image per page) often adds front matter, extra cover pages, or blank backs and can push the total higher. Conversely, a reflowed PDF or a font-tweaked export could compress the text and shave off pages. If you want the exact number for a specific file, open it in a reader and check the page indicator or Properties — that’s definitive for that file.
For me, the number is less important than the ride — if you're rereading 'Allegiant' you just want to be careful about which edition you're comparing (US vs. international printings sometimes list different page counts). If you're collecting, go by the publisher metadata or ISBN to match physical and digital counts. I usually keep a note with the ISBN when I download or buy an ebook so I know which edition I'm holding.