Whio is an EPUB and PDF reader aimed at people reading technical books on iPhone or iPad. It gives prose and code separate typography controls, preserves indentation in code examples, and supports syntax highlighting and horizontal scrolling for long lines. Optional reading aids include a reading guide, a focus window, and letter distinction settings. Readers can highlight passages, add notes and bookmarks, search saved material, and export their notebook. Whio includes original technical books that the listing says can be read in full at no cost; imported DRM-free books have a free preview, with full access available through Whio Unlimited. The app offers both subscription and one-time purchase options for that upgrade. Confirm the current offer in the App Store before buying.
