Page Viewer Web Part File Link Format

Steve_Penner Which version of SharePoint are you using?

If you are using SharePoint online modern experience, you can use the File and Media web part and provide file URL in this format: 

https://<tenant>.sharepoint.com/sites/<siteName>/<libraryName>/MyWordDocument.docx

Use this URL in the web part. Next time when you edit the file locally on your system, you can upload the file with same name and replace it in your document library so that it will work without any issue.

You can get the URL for your document from details pane like this: 

For details steps, check my answer at: How can I show a sub folder from another SharePoint site? 

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