The OneDrive PDF conversion is fairly limited, so your best bet may be the Plumsail Documents connector. If you could provide an expanded screenshot of your Flow and steps, and of any detailed error messages you're receiving we could likely better assist you.
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You can use the Muhimbi Flow Connector to Convert Email attachments(in your case .png file) to PDF. For details on how to use Flow to PDF Convert email attachments to OneDrive, DropBox, Google Drive etc, http://blog.muhimbi.com/2017/03/use-flow-to-pdf-convert-email.html
Gustavo, thank you very much for that link! I was able to make a PDF from a PNG file. However, it seems that the PDF is created with portrait orientation. My PNG files have landscape orientation. Is there a method to create the PDF with landscape orientation?
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