okie cokie
one way to try is:
1. open yer pdf (fairly simple so far)
2. click File
3. hover over Export
4. hover over Image
5. click JPEG
6. choose a destination folder or create a new one
7. click save
8. go and make a cuppa while you wait
9. close your PDF
10. open Acrobat
11. click Create PDF
12. click Create PDF From Multiple Files
13. click Add Folders
14. choose the folder from step 6.
15. click Smaller File Size (lower quality optimizes PDF files)
16. click Next
17. click Create
18. drink the cuppa from step 8

19. click Save
20. name your new, smaller PDF and save it somewhere
if that's still too big.... ummmmm.... go through all the exported JPEGS one by one and crop them as much as you can, then make a new PDF from the cropped images... OR... repeat the whole above process with the new, smaller PDF until you get the desired filesize.. image quality will drop significantly though... I'm assuming it's a PDF of Origami diagrams...
have fun.