I have had good luck with the PDF compressor at http://smallpdf.com/compress-pdf to downsize large PDF's before uploading to the server for everyone on the forum to use.
Example: The Firan Owners Manual here was emailed to me as a 25mb file and SmallPDF compressed it quickly and easily to 7.5mb. I was then easily able to upload it from my computer to the forum server via the Upload Attachments button in the upper right of my post (2 buttons left of the smiley).
Example: The Firan Owners Manual here was emailed to me as a 25mb file and SmallPDF compressed it quickly and easily to 7.5mb. I was then easily able to upload it from my computer to the forum server via the Upload Attachments button in the upper right of my post (2 buttons left of the smiley).