You can add a PDF document to your site by using Google document viewer service.
Here is a good HowTo video - http://www.steegle.com/websites/google-sites-howtos/embed-drive-pdf
1. Add to Google Docs: First you will need to upload the document to your Google Docs account.
See here how it can be done - https://support.google.com/drive/answer/2424368?hl=en.
2. Making the document 'Public':
Once the uploading process has been completed, the document should be opened automatically.
First, you will need to make the document Public. This can be done through the Sharing settings of the document which may be found in the document details ( for more see - https://support.google.com/drive/answer/2494886?hl=en)
In the sharing settings, Click on 'Advanced'
and change it from Private to Public - see images:
3. Getting the document code:
To get the HTML code, that you will later need to embed on your site, go back to the PDF viewer, press the 3 dotes button for more options, and choose 'Embed Item...' :
* If you don't have the two first options on the menu, make sure you are viewing the PDF in the Pop-Out mode. If you are not, you will see 'square&arrow' button on the upper right side. Press it, and go to Embed Item:
4. Embedding the code on your site:
The 'Embed Item' window with the PDF viewer's HTML code will be opened.
Copy the code, and paste it into an HTML code on your IM site through Add Element > HTML (for more, please see - http://imcreator.com/create-a-website/html-embed-cod)
You can adjust the viewer size by change the HTML element size.