Hi, the problem is that PDFs don't get attached to posts. I look into Multimedia and doesn't see any PDFs, but the PDFs are generated inside /tmp.
If I create a NEW post and enter a title but no text, the autosave feature of the edit screen triggers the plugin, and it generates a PDF file named ".pdf" that gets attached to the post. When some text is entered and the post is saved, then all works well and a new PDF gets attached to the post.
The problem is that it doesn't work with existing posts. When I hit update the PDF gets generated inside /tmp but doesn't get attached to the post.
Disabling and enabling the plugin does generate all PDFs again inside /tmp, but doesn't attach them to their posts.
I have changed my code for displaying PDFs to match yours (I did this before):
get_latex_url( 'single_post', get_the_ID() ) ): ?>
<a href="<?php echo $latex_url ?>">PDF</a>
and obviously now the link is not visible. Previously it generated a link to the post when it couldn't attach the PDF.