Hi @A Falc,
I tested your problem in my side and my PDF files are not zoomed (My SharePoint App Version is 4.49.0). This issue is related to your mobile phone model and SharePoint App version. I'm sorry there is no way to set the viewer of the PDF files at the moment. Maybe you can change the version of SharePoint App or use a different model of phone. Thank you for your tolerance and understanding!
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