Reading a PDF comfortably on a tablet or phone

PDFs are supposed to be miserable on a tablet. Mostly they are, and mostly it is for one reason that takes ten seconds to fix at conversion time and is impossible to fix afterwards.

The mistake

Almost every PDF you have ever opened on a tablet was made for a sheet of A4 paper. Your tablet is not a sheet of A4 paper. It is smaller, a different shape, and held much closer to your face.

A PDF reader has exactly one move available: scale the whole page to fit the screen. So an A4 page designed for 90 characters across, read at arm’s length on paper, gets shrunk onto a 10-inch display, and the type arrives at a size nobody would choose. You zoom in. Now you can read it, but the page is wider than the screen, so you pan left and right on every single line. That is the experience people mean when they say PDFs are bad on tablets.

The fix, which is counter-intuitive

Make the page smaller. Do not make the type bigger.

This surprises people, so here is the arithmetic. Suppose a 10-inch screen:

Setting	Characters per line	Effective size on screen
11pt on A4	~90	tiny
14pt on A4	~70	slightly less tiny
11pt on a tablet-shaped page	~55	comfortable
11pt on a phone-shaped page	~35	large

Increasing the type size makes the page hold fewer words, but the page is still scaled to the same screen, so you gain very little and add a third to the page count. Shrinking the page holds fewer words and gets magnified more when it is fitted to the screen. The page size is the real zoom control.

The practical version:

• Tablet — page size “Tablet screen (4:3)”, 11pt, narrow margins.
• Phone — page size “Phone screen (16:9)”, 12pt, narrow margins.
• Something that also prints — A5, 11pt. A compromise, but a far better one on screen than A4.

Narrow margins because screen margins are wasted: nobody holds a tablet by the paper.

Turn the bookmarks on

On paper you find a chapter by riffling. On a screen there is no riffling, so the PDF outline, the sidebar list of chapters, is how you move around a long document. It costs nothing and every serious reader shows it:

• Apple Books — tap the contents icon, top left.
• PDF Expert, Xodo, Documents — a bookmarks or outline panel.
• Adobe Acrobat — the bookmarks tab down the side.
• Google Drive’s viewer — the contents button.

The generated contents page is worth having too, because its entries are tappable links that jump straight to the chapter.

Getting the file onto the device

However you normally move files. AirDrop to an iPad offers to open it in Books. On Android, drop it in Drive or the device’s own storage and open it with whatever reader you like.

There is no service in the middle here. The PDF was built in your browser and it is sitting in your downloads folder. Nothing was uploaded, so there is nothing to sync and no account to make.

When you should not do any of this

If you just want to read the book, and your device opens EPUBs, read the EPUB.

That is the honest advice. An EPUB reflows to your screen, your font and your chosen type size, adapts when you rotate the device, and remembers where you were. No PDF can match that, because a PDF’s pages are fixed by definition, which is the entire reason it is useful for everything else.

Convert to PDF when you need something only a PDF gives you:

• Fixed page numbers, to cite or to discuss with someone reading the same file.
• Annotation in an app that takes nothing else, which is most of them.
• Handing it to someone whose device will not open an EPUB.
• Printing, obviously.
• Archiving, where a format that will still open unchanged in twenty years is worth more than one that reflows.