If you want a straight-up, no-cost route, I usually point people to the big public-domain libraries online. Project Gutenberg hosts older English translations of 'Dante's Inferno' (those Longfellow-era versions and similar nineteenth-century translators), and you can download them in plain text, ePub, or Kindle formats. Internet Archive and Google Books are excellent for scanned editions if you like paging through old introductions and marginalia. For audio, LibriVox has volunteer-readings of public-domain translations, which is great for commuting or pacing the rhythm of Dante's lines.
If you prefer modern, annotated translations that explain the historical references and theological bits, look for editions from major publishers (Penguin Classics, Everyman, Oxford World’s Classics). Translators like John Ciardi, Allen Mandelbaum, and Robert Pinsky each bring very different flavors—some aim for poetic energy, others for clarity and notes. Your local library’s app (Libby/OverDrive/Hoopla) often has both free ebook and audiobook versions of these newer editions, so you can try different voices without buying them.
Personally I mix and match: a free public-domain text for baseline reading, plus a modern annotated edition when I want the cultural and historical background. It makes Dante feel both raw and wonderfully alive to me.
If you're hunting for a free PDF of 'Dante's Inferno', the good news is that the original text is in the public domain, so reputable sites host legal downloads. My go-to is Project Gutenberg — search for 'Divine Comedy' or 'Dante Alighieri' there and you'll find several translations (Henry Wadsworth Longfellow's translation is a classic public-domain option). You can download in plain text, EPUB, or sometimes PDF; if a PDF isn't provided, you can convert an EPUB or text file to PDF with a reader program.
Beyond that, I like the Internet Archive and Open Library because they often have scanned editions (complete with older commentary and illustrations) available to download as PDF. Wikisource is another neat place for public-domain translations with clean text. Just watch out for modern translations: many contemporary versions with helpful notes are still under copyright, so those won't be legally free. I usually grab a public-domain translation for quick reading and then buy a modern annotated edition if I want commentary — it's a balance that works for me.