Perhaps the easiest workaround is to generate an image (jpeg, png, tiff, gif, bmp) of the part of the article you are interested in and insert that image. Many image manipulation software and some pdf viewers will allow you to do this, but the quickest way is perhaps to take a screenshot.
For posting links to complete files, you currently have to find your own hosting solution, which unfortunately leads to inevitable link rot. (ThisThis used to be the case for images too but now SE exclusively uses imgur to host images inserted in posts.) If there is enough interest across the network, there is a chance that SE would try to do something similar to the way they now handle image filesfor documents.
I'm assuming this is material which is not available publicly anywhere. If it is published, either as a preprint or in a journal, then the best solution is to post a doi link or a link to the arxiv. That way, our robots will pick up the link and generate suitable backwards links to your question, when possible. We are currently working on easier methods to insert proper links to published and prepublished material but we don't expect that to be ready for a few months.