To old fashioned print media types out there, webcomics are completely baffling. The most common argument you hear is “Why would anyone want to buy your work if you're putting it online for free?” And they probably would have a point if we lived in a world where the entire world had free high speed wifi but until then, there will be people who want to read through comic archives and might not have access to the internet everywhere they go. Printed versions are definitely an option that isn't going anywhere anytime soon, but they do represent a risk for webcomic authors who haven't built a massive audience yet. A safer way of providing offline archives is the ebook, which can be made with software available online for free.
If you have a Mac, follow these instructions by Ryan Estrada to make a .CBZ, .CBR, (basically, readable .ZIP and .RAR files) and .PDF copy of your comic as well as where to sell it (though selling them via PayPal takes less of a cut than Gumroad, but Gumroad's more convenient so consider if it's worth the trade off). For Windows users, the instructions for a .CBZ and .CBR are the same, but if you want a .PDF, you'll have to get CBR and CBZ to PDF, a lightweight program that does exactly what the name suggests. Click “Browse,” look for your file, select it, then click “Convert.” You can change the page size and border size in settings, but that's it.
There are more robust programs that can convert images to .PDF files for free, but from what I've seen, a lot of them come with toolbars, unwanted programs, and change your default search engine and home page to dodgy websites that are a pain to remove. If you need something with more features, read up on it first, look for a download option that's on the developer's site instead of the larger download sites like Download.com, pay attention during the installation process, and scan through the end-user agreement for anything suggesting that other programs will be installed. I've had to remove crapware from other people's computers more times than I would like, so I'm not touching these programs. If you want to try any of them out, you're on your own. For any other reader filetypes, try Calibre.
Besides direct sales on your archives, ebooks provide a lot of other opportunities. Doing a Kickstarter or a Patreon and want to do a low-level perk that's more substantial than a heartfelt thank you? Offer an ebook. Or, considering how easy it is to make them, sell different versions with more content like exclusive comics or commentary for a little more. Or, sell supplementary material separately as their own books. Since there's no risk of losing money or storage space on digital files, you can freely experiment with different payment methods and products until you find what works.
Note: If you have any recommendations for free PDF programs or instructions for Linux users, feel free to post in the comments and I'll add it to the article.