Hi,
I want to make it clear that @pdftron/webviewer and @pdftron/pdfjs-express are different packages. We do not support @pdftron/webviewer on this forum, and you will have to contact PDFTron support for any further support regarding @pdftron/webviewer
If you are using @pdftron/pdfjs-express, you will see the PDF.js Express watermark, if you are using @pdftron/webviewer, you will see the PDFTron watermark.
When switching back and forth between packages, please make sure you are deleting node modules and any other files related to the old package.
Thanks,
Logan