PDF file size bloated wildly

Emergency situation. I’ve had to delay publication because of a critical problem and my entire business depends on fixing it in the next two days or less.

Last year the on-screen-only PDF version topped out about 67 MB. Big but manageable. This year it’s over 165 Mb. This year was slightly bigger (a few more pages added but all vector animations and text). The size of the full .indd file went up from about 490 Mb to 692 MB. When I save-as it reduces to 386 until it’s opened.

Adding about a dozen vector images and text frames shouldn’t add 100 MB to a PDF, when downsampling is deeply constricted in size reduction (96/144, Medium resolution). I have an absolute ton of internal and external hyperlinks, cross-references and so on. Graphics aside from the cover are reasonably small for the most part, although there may be a handful that are a bit bigger.

What can I check and compress to make this a lot smaller? My hosting server will not allow a file that big, and I doubt my customers want a 160 Mb file on their phones and tablets either. My planned-weeks-ago book launch tonight was cancelled and I’m beyond panic right now.