You can just add a link or you can post the PDF for all to see
Look at the 1st attachment Picture,
Once you've posted the link, Highlight it and then click on the PDF icon, 2nd row down , 2nd in This will add the [pdf] tags to the front and end of post.
Thats its your PDF is on the post for all to see..
The 2nd attachment shows how to download, Firstly you move the mouse cursor to the top of the PDF and you'll see a menu appear, The 3 icons to the right are the ones you want, 1st is the Rotate, 2nd is the Download, and the last one is the Print, But be careful because some of these PDF's are pretty large in terms of Page.
To make the attachments larger, just double click on them