I notice that PDF text documents that I load to Research Gate as preprints are poorly imaged and not easy to read. Is anyone else experiencing this and have you any best practice tips to avoid this issue?
I never had problems with reading PDF documents online at RG. This may be an issue of your browser. I had a look at your preprint https://www.researchgate.net/publication/369507343 as an example, and I do not see any problems, it is well readable. In any case users may download the file and read it offline. RG does not change the files after uploading.
In fact, very unsightly. However, I do not have such a problem nore with Firefox nor with Microsoft Edge (newest Version 112.0.1722.34) on a Fujitsu laptop with Windows 10 (tested right now with your PDF), and also not on other computers with other documents. You may try to contact RG's support team at https://www.researchgate.net/contact.
Yes it is not look good. While Wolfgang R. Dick might be right another possible question is to check how you generated the pdf and what the font selection you made. If you used word processor then the quality of PDF is not that good. If you use latex and family and you can change the font scheme. I try to use helvetica family or modern font that do not have extra fancy. There more complex method like masterpdf which I don't recommend.
Can tell how did u generate the PDF? I am not expert in docx but I have some understanding in latex and family. The definition of the font should be somewhere in the beginning the pdf file. In your case, the fact changing the font did not help tell me that there is another element in PDF that cause the problem. I assume that you do not want to debug the pdf. Is there a way u to convert the file to a different langue and do the conversion to PDF. For example try doc rtf and rtf to pdf. I had to deal with docx and ms word tends to create messy and encrypted pdf. may by load it to LibreOffice that can generate a better pdf. Not all the pdf are the same.