By following the steps below we can attach PDF file to the M2 site
Go to admin.>stores>configuration>MageWorx attachments>Manage attachment>Add New attachment. Give a name for the file to be attached. Specify the download limit, upload the file> select the customer group> click active.
Now to add the file to the corresponding text in the website, select the particular category or post (Admin> catalog>categories). In the content make it as HTML format. Search the text where the link is to be added and then add the HTML code as in the format given below:
<a href=”{{media url="mageworx/downloads/attachment/file/t/f/tfs_procurement_case_study_jan_2015_1_.pdf"}}” download=””>Download</a>