PDF Expert

PDF Expert is the PDF reading, annotation, and editing app built by Readdle, a Ukrainian software company Denys Zhadanov bootstrapped from Odesa in 2007. It grew to $30M+ ARR with 200+ employees by making the fastest, most capable PDF experience on iPad, iPhone, and Mac — with tools for annotating, editing text directly in PDFs, merging documents, signing contracts, and filling forms. Over 130 million people have used Readdle's apps, which also include Spark (email), Scanner Pro, and Documents. PDF Expert's iPad version became the gold standard for paperless workflows — attorneys annotate contracts, students highlight textbooks, consultants mark up proposals — all with an Apple Pencil experience that felt indistinguishable from writing on paper. The Mac version offered full PDF editing (change text, images, and page layout directly in the PDF) that competed with Adobe Acrobat at a fraction of the price. Readdle's Ukraine-based development team combined Western product sensibilities with Eastern European engineering efficiency, creating an unusual competitive advantage in consumer productivity software.