Epson ACULASER C3800 - Manual (Page 122)

Using the Printer Software with Macintosh 122
EPSON AcuLaser C3800 User's Guide
To make a bitmap watermark
Before making a custom watermark, you should prepare a bitmap (PICT) file.
For Mac OS X users
1. Open the Print dialog box.
2. Select Printer Settings from the drop-down list, and select the Basic Settings tab.
3. Click Stamp Function.
4. Select the Watermark check box, then click Watermark Settings.