Hey @essy!

I don't believe there is a set property on the pdf viewer component at the moment (although this is a great feature request, I'll write this up internally). You can however store this URL in a temporary state (link to our docs on this here) and display the results by triggering a REST query to the URL and displaying the results in the pdfViewer:
In this example app, each of my buttons have an event handler that changes this state that looks like this:
Next, after the URL is changed in temp state, I have a REST query that retrieves the PDF:
The return of this will be Bast64 binary so we can display the following in our PDF viewers base64 input:
{{getPDF.data.base64Binary}}
Do you think this could work for your use case here?