We just recently got this information ourselves. This feature used to be a preset on the 7345, but was missing from our new 7545s. I've pasted the documentation Xerox provided us below - sorry, it's from a PDF so the formatting is a bit gross.
Note also that a current software release for the 75xx models actually includes ID Card Copy as a service you can display or not. We were happy to see this, but could not use this release due to a problem it caused with our expense recovery terminals. The release that contains the ID Card Copy feature is 061.121.221.20901.
XEROX ID CARD COPYING Create the ID Card Copy Function and Save the Settings for Future One-button Access The following procedure is used to create a one-button function to copy both sides of an ID Card or similar two-sided document onto one side of a sheet of paper. 1. Press the [Services Home] button on the Control Panel, and then select the [Copy] button on the Touch Screen. 2. If necessary, select the [Copy] tab on the Touch Screen. 3. Select a paper tray containing the required output paper size: Long Edge Feed (LEF) Letter (216 x 279 mm / 8.5 x 11 in.) or Long Edge Feed (LEF) A4 (210 x 297 mm / 8.3 x 11.7 in.). 4. Select [2 > 2 Sided] button. 5. Select the [Layout Adjustment] tab. 6. Select the [Original Size] button. 7. Select the [Preset Scan Areas] button. 8. Select a paper size that is half of the size of the output paper selected in step 3. Make sure to use the opposite orientation: Short Edge Feed (SEF) Statement size (140 x 216 mm / 5.5 x 8.5 in.) or Short Edge Feed (SEF) A5 (148 x 210 mm / 5.8 x 8.3 in.). 9. Select the [Save] button. 10. Select the [Output Format] tab. 11. Select the [Page Layout] button. 12. Select the [Pages Per Side] button. 13. Select the [2 Pages] button. 14. Select the [Save] button. 15. Select the [Job Assembly] tab. 16. Select the [Save Current Settings] button. 17. Under the Setting menu, select an available slot. 18. In the Setting Name text box, enter a name, such as ID Card Copy 19. Select the [Save] button. 20. Make a copy using one-button access. Make a Copy of an ID Card Using One-button Access NOTE: This function will only work if you have created the ID Card Copy function and saved the settings for future one-button access. See the Related Items below for additional information if you have not already set up the ID Card Copy function. 1. Press the [Services Home] button on the Control Panel, and then select the [Copy] button on the Touch Screen. 2. Select the [Job Assembly] tab. 3. Select the [Retrieve Saved Settings] button. 4. Select the Setting Name used for the ID Card Copy function, and then select [Load Settings]. 5. Raise the Document Cover. 6. Place the ID Card to be copied face-down in the rear, left corner on the Document Glass, and then gently lower the Document Cover. 7. Press the [Start] button on the Control Panel and wait for the “Ready to scan side 2” message to display on the Touch Screen. 8. Raise the Document Cover. 9. Flip the ID Card over and lower the cover. 10. Press the [Start] button on the Control Panel.