This is because transparency has been used for the watermark text.
In order for printers to print transparent watermark text they must support Alpha Blending. Most printers support this but some do not.
For this reason we recommend that you DO NOT use transparency in text watermarks unless you are using Lizard Safeguard in a controlled internal environment where you are sure that all printers support Alpha Blending.
The simplest solution is to use a different colored font (say a silver color) for the watermark text to ensure that it is always printed.
Also, if transparent text is used, then the more watermark text you use the slower the page rendering will be in the Safeguard viewer. For this reason it is recommended that if you do use transparency then you use as a maximum one line of text. Reduce the font size if necessary to minimize the amount of text used.