If you’re going to embark on the POD – print-on-demand journey then, you’ll certainly need something which a resizing tool to suit the various products, as one size DOESN’T fit all!
There a few in the online marketplace, some actually cost a few quid (not required) and a few are thankfully free 🙂
The one I use for all of my Zazzle products is from Promo.com tools section. It’s free and only a name and email address is required in order to avoid the annoying captcha codes.
This website is ideal for platforms including Redbubble, Society6 and Zazzle (my favourite”).
Page Link => https://promo.com/tools/image-resizer/