Cách tạo Biểu trưng độ phân giải cao (Canva Pro)

I am using Canva to create PNG's for my Etsy customers to make waterslides or sublimations. Is there a way to make the DPI 300 while still maintaining the transparent background? I have been downloading a design in canva as a PDF print(to get the 300 PDI)

And then (my husband) put it through a PDF to PNG converter and then changed it back to transparent by hand by clicking on each spot on the image manually to make it transparent. I also need to figure out how to increase the size with out it getting fuzzy.

There are all sorts of people selling transparent PNG's on Etsy…are they using different software than Canva?