There is no limitation of character size for QR codes in our app. However, please keep in mind that the size of the QR code increases with a rising number of characters behind. As the maximum height of an imprint is 14 mm, in terms of readability of the QR code once it is printed should also be given.
We tested QR codes with different character sizes and even ones with 60 or 80 characters were still well readable by our QR code readers. Nevertheless, please consider that readability of the printed QR code depends also on the quality of the QR code reader of the device, mobile phone, etc. used.