A mug with printing on both sides is not one design with two halves. It is two sides, each with its own real size, its own layers and its own print file. Once that is clear the recipe is short, and the only real decision is how much of the second side a shopper gets to touch.
Build it
Add the second surface
On the product, add the second printable area with its own size in millimetres. See manage a product’s sides.
Design both sides together
Build the front and the back before you make anything editable. It is much easier to balance two sides while you can still move everything.
Decide who edits what
Mark the fields on the side or sides the shopper controls. Leaving the back fixed is a legitimate product, and a simpler one to sell.
Order the questions
In the customer form dock’s Form view, drag the fields so one side’s questions are finished before the other side’s begin. A shopper who is asked about the front, then the back, then the front again will abandon.
Check both files
Every surface produces its own set of files, so a test order should give you two. If it gives you three, you have a surface you forgot about.
How much to hand over
The middle option is usually the best product. One editable side gives the shopper the feeling of having made something, and gives you one proof to check rather than two.
Common questions
Can one design span both sides?
No. Each surface is its own design area and produces its own file. A wraparound is two coordinated designs, not one wide one.
Do I have to personalize both sides?
No, and usually you should not. Fixed artwork on the back is normal and keeps the product recognisably yours.
The shopper filled in the front and left the back empty.
Mark the back field Required to check out if it must be filled. Otherwise a blank prints as a blank.
Why do I get two PDFs and two PNGs?
One pair per surface. That is the expected output for a two-sided product.
Can I add a third surface later?
Yes. It is a design edit rather than a rebuild, though a new surface starts empty and needs its own artwork.
Next
Read manage a product’s sides for the side settings themselves, or from design to print file for what each side becomes.