First you must upload the documents to your DOCUMENTS area. You can learn how to complete that here:

Once your documents have been uploaded you will then click the VIEW button to the right of the document you wish to include in an email notification or content snippet and a lightbox will open.  You will copy and paste the link in orange or short link if you are using the link internally. 

You will then go to SETTINGS>>CONTENT AND LETTERS and click EDIT for the content snippet you wish to add the document to. 

Then you will incorporate the text you wish to link the download to, for example you could include text like "Download our Uniform Policy" then highlight the text you wish to be the link and click the INSERT / EDIT LINK icon.

This will open a lightbox where you paste in the document link or document number from the previous step. 

You will click OK on the lightbox then click SAVE in the content snippet.