[OJS] Add preview PDF article

We need your help. I want to view articles on their personal pages from downloaded PDF files (which are used in proofs).
There was a problem in the code that would form a link to the downloaded PDF file of the article.

The proofreader has this link, but I don 't really understand how it is formed.
All changes are made in the article_details file.tpl.
OJS is used.
I plan to insert a PDF using a simple html code in the drop-down menu.
I didn’t find any built-in features for creating such an object. if possible, specify what to look for and how to configure it in the article’s detail code
I would appreciate your help.

Can no one help me in this question?