If you want to use the "PDF Viewer" component with static content (just one PDF-file), you will have to store the pdf-file in a database or SharePoint.
You could try to upload a file to Power Apps Media, but Power Apps will refuse to upload a pdf file as it expects media files. 🤨
Hower; if you just rename the pdf file extension to .png, you could upload the file to Media and just use the filename in the Document property of the PDF Viewer component.
Viola! It Works.... 😂