How to upload and link a PDF file to your question.
Click any of the "Upload Image/File" links to upload the PDF file. Note that location of the file.
Typically it will be "UploadedImages/yourfilename.pdf"
Make sure the file has no spaces or special characters in the filename that could potentially break the link.
Then in your question text box, click the link button, or click the "Source" button and paste in the link
<a target="_blank" href="UploadedImages/YOURPDF.pdf">Click Here to Open PDF</a>
Then click save.