What is the minimum screen size for PDF documents?

The greater the screen size, the greater the flexibility

Is 10.3-inches the bare minimum to view PDF documents comfortably? The answer depends on the nature of the PDF document viewed. Many humanities and social sciences books are B5-sized and can be viewed comfortably on a 7.8-inches screen. I would say a 7-inches e-reader, with the right software features, can display B5-sized documents in portrait mode comfortably. On the other hand, science articles, for example, that are often two-columned need a larger screen (ideally, two-column documents require a 13.3-inches screen to be viewed comfortably).

Another factor is the software used to manage a PDF document. Are there crop features, the possibility to pinch-to-zoom, text reflow and different ways to navigate documents with complex layouts? For example, Onyx Boox supports the ability to crop a PDF document in four ways to split the page's content so it can be navigated separately. This feature is helpful with two-column documents or scanned books with two pages scanned as one.

Simply put, the greater the screen estate, the greater the flexibility when dealing with PDF documents. Nevertheless, it is possible to read many PDF documents on a smaller screen with the right software features.