truly and sincerely every time i go to download a comic i bought from someone on gumroad or w/e and it's a pdf i want to scream. pdfs suck so bad. please for the love of god use cbz or cbr for comics.
cbz/cbr is so good, it's literally just a folder full of named and numbered pages saved in a standard image format like .png or .jpg, then you compress it to a .zip or a .rar and rename the file from .rar to .cbr or .zip to .cbz
then anyone can just use a comic reader on a computer or tablet or ereader to open and read it or they can unzip it for the individual images, and you can make the image files inside big so the reader can just scale them to the device!