Follow this tutorial to enable auto printing in PBU.
Make sure printing is enabled in your event on the Event Manager website HERE. Select the Printing option on the left of the event settings page, then click on the Printing tab at the top. Check the box labeled Enable Print.
Submit your event and refresh your events list in the Helper. You can also select the Just Printing event in the Helper to skip going to the Event Manager page entirely.
Open Photo Booth Upload, click S for Settings, and select the PPU/Printing tab at the top of the screen. Select the printer that you want to use from the menu at the center of the screen.
On the right side of the screen there is a box titled Auto Print. Here you can select the settings for auto printing. You can either decide how many copies of each photo to print, or use the software to print one copy for each face that it counts in the image. You can also disable auto printing for GIFs and Morphs.
At the bottom of the menu, click the green START Auto-printing button.
You are all set to begin auto printing at your event.
Auto print Lag
Sometimes a corrupted database file will cause a long delay during auto printing. To remedy this, delete your database file in your Photo Booth Upload Program Data folder.
Delete Program Data for PBU
-Exit PBU and PBU Processor (if running, PBU processor is a pink on in the system tray near where the Helper would be. Right click and select Exit)
-Open C Drive
-Select View Options and check Hidden Items
-Select the folder called Program Data
-There will be another folder for Photo Booth Upload
-Inside that folder there will be a DB folder
-Delete the contents of the DB folder