Pdfs with safari

Hi,
I've had to do a lot of research for school lately, and most of these research articles are PDFs. When I open the articles I open them in a new window in Safari, and sometimes I am able to read them. Other times, The last thing I can find on my screen is the vertical splitter. All of the other buttons are still there, e.g. new tab minimize and close, but I am unable to find the window to read the PDF. If I turn voiceover off and have a friend click on the PDF, voiceover will then read it but I cannot figure out how to do this myself.
Any suggestions?
Thank you

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Thank you

Thank you so much for the suggestion, but unfortunately this was not successful. It's not a downloadable PDF they just open in the web browser. The PDFs themselves are accessible because once I turn off boiceover and a sighted friend clicks on the PDF, voiceover can read it in the browser.