At work, one of the attorneys had a humongous PDF document she needed to email a lot of other attorneys outside the office. I tried extracting pages with an old version of Adobe Acrobat (v5), but the original file still kept the same size (despite having deleted the pages).
With open source (free) software, I split the document into two separate files in a couple minutes.
Once you install that, open your PDF document (original_superlongdocument.pdf) in your preferred reader. Now, go to File > Print. Change your printer to PDFCreator, then change your page range so you’re only “printing” half the document. If you have a 1,000 page document, set it to 1-500.
Follow the prompts and save that new PDF file — just not over your original. (superlongdocument_a.pdf)
Now, repeat for pages 501-1000 and save that one with a different filename. (superlongdocument_b.pdf)