I have a problem with watermarks on my PDFs after installing - end user products

After installing I still get watermarks on all my PDF files.

You have not entered your serial number or not entered correctly - please ensure you copy/paste the serial number from your receipt into the installer for the correct product and do not type.
If you purchased your product from a retail store and therefore must type the serial number - commonly the character 'I' and the number 1 are confused and the letter 'O' and the number '0' - ensure you have not confused these.

If you own the full PDF-XChange PRO bundle and creating new PDF files functions as expected - but the PDF-XChange Viewer operates in 'FREE' mode only, copy/paste your serial number into the PDF-XChange Viewer PRO option under the Edit Menu -> Preferences -> Registration and all should be well.

You thought you had purchased PDF-XChange PRO - but in fact you purchased the PDF-XChange Viewer PRO ! If your serial number begins PVP20 - you do not have PDF-XChange PRO - but the Viewer PRO -as such you are not licensed to use a product that can create new PDF files from other software applications such as MS Office, Internet Browsers etc!  You will need to upgrade to PDF-XChange 4 PRO or purchase PDF-XChange 4 Standard or Lite.

You have downloaded the latest Version 4 release - but your version 3 serial number is not valid and PDF-XChange operates in trial mode ?  Your version 3 serial number is not valid, see here for info on how to progress your discounted upgrade