When creating a module, you can user "Inner File" to provide a link to a document in the Documents application.
With the use of embed code, it is possible to view the PDF in a small window on the module's page.
Navigate to the document you wish to use. When viewing it, take note of the number at the end of the page's URL:
Create or edit your E-Learning module, and change its type to "Embed Code"
Copy in this:
<iframe name="previewIframe" src="/intranet/documents/preview.php?doc_id=213" style="width:100%; height:500px;" frameborder="0"></iframe>
Change the number highlighted in red to the number obtained in step 1.
Your document will display as seen in the image below.