iOS 15 brings significant advancement to viewing and annotating PDFs. When you open a PDF on iPhone, whether in Files, attached to an email, or elsewhere, you can now view page thumbnails on the left and make adjustments to the pagination, just like in Preview on the Mac.

Show Thumbnails

Open a PDF with multiple pages. Although invisible from the document displayed, put your finger on the left edge of the screen and swipe to the right to reveal a sidebar with the page thumbnails. To dismiss the sidebar, swipe to the left from anywhere to the right.

The interface is a little rough around the edges so far, so it wasn’t obvious to me that the sidebar is available nor how to make it go away. Swiping the right edge of the sidebar when it’s visible has no effect but swiping elsewhere on the screen to the right of it does the trick. Scrolling the document is another way to dismiss the sidebar.

Page Actions

With the sidebar in view, you’ll see an ellipsis button  on the current page. Tap it to show a menu of choices to rotate, add, or delete pages.

You can insert a single blank page, merge a whole additional PDF file, or scan pages and add them to the document. Added pages will appear below the current page.

If you make a mistake, just swipe left with three fingers. This “Undo” command is available throughout iOS. Or, you can tap the marker tip in the top right to enter Markup mode and then the undo and redo buttons are at the top.

Markup Tools

Markup provides several additional tools to annotate a PDF. Tap the marker tip to toggle Markup mode and a number of implements appear at the bottom.

The first three are a pen, a thick marker, and a thin marker. You can use the color picker on the right to choose a color or the eyedropper to match a color in the document.

The next tool is an eraser for removing markup. Then comes the selection tool: swipe across one or more shapes or annotations to select them, and drag the selection or tap to choose an action from the menu.

The ruler tool toggles the ruler while any other tool is active. You can drag it to measure objects on the page, use it as a straightedge, and use two fingers to rotate to angles between 0° and 90°.

Finally, tap the plus button ⊕ to add other elements: text, signature, a magnifier loupe, and various shapes. Learn more about markup.

Your iPhone provides a lot of power and flexibility to annotate a PDF file, even if you can’t directly edit the original content. What will you do to mark up the documents you receive?