If you import an architectural drawing PDF into GoodNotes, you might see frames/boxes around the text in it. The same PDF shows no such frames when viewed outside GoodNotes.
It's a known issue that seems to happen to this specific type of PDFs, likely created in AutoCAD. Until there's a fix, a simple workaround is to open the file in Mac Preview and choose File > Export as PDF... and the result PDF won't have this issue in GoodNotes. Alternatively, you can open the original PDF in Chrome, choose Print, but choose "Save as PDF" in the Destination option.