When preparing your PrintShop Mail Design document to be printed through PrintShop Mail Web, it is important to take into account which printer you have selected to setup your document as well as the one that will be used to finally print out the file.
The main concern is your page setup, including your page size and margins, tray selections, etc. For example, say you designed your document on white letter-sized paper which has a half-inch margin. The second page (or layout) of your document however is printed on blue paper which is called using a tray selection. The printer you selected is from one major manufacturer.
On the PrintShop Mail Web server, this printer is not installed. You are aware of this fact and fully intend to print to a different one that is not from another manufacturer. This other printer does not have the same tray names and the margins is only a quarter-inch on the Letter-sized paper.
What will happen when you send your document and start a new print job depends on a number of technical factor but the results may be different than what is expected. Your second page may not come out of the right tray or your contents may be shifted higher and to the left because of the difference in margins.
To resolve the issue, you would need to have the same driver on your PrintShop Mail Design machine as the one you ultimately output to on PrintShop Mail Web. If the printer is not accessible from the computer, you can simulate this by simply installing the driver and point it to a port that is not in use (either LPT or TCP/IP port). You won't be able to actually print to it, but your page setup will still be valid when your document ends up in PrintShop Mail Web.