Popularity has it's price, that price is $3 per gig over your quota, (YMMV) those words have brought fear and dread to more than one web user over my support career. Yes if you host a 1 meg file, and link to it from your home page, it will blow thru your quota if you become popular, so from this side of the help desk, here goes, "How to share your PDF's, have analytics, and spend $0 on hosting"
1) login to your gmail account, then click on documents top left,
2) click the Upload button, Select the files you want to upload, and click open
3) Navigate to the new file and click on Share > Sharing Settings > Change
4) Set to "Public on the web" and click Save.
5) Copy the link for IM or email and use that as the HREF for the link on your site.
Has many more uses than just sharing a paper airplane.
What is Not Measured, Is Not Managed,
Make sure to add your Google analytics info to docs so you can know when you go viral!
1) Google Docs > Settings > Editing > Document Tracking, add your UA# and click save.
2) Contact your web host and have them 301 redirect the old pdf to the new Google Docs link.
You are now free to spend your cash on other things.