How to Change PDF Annotation Opacity

Annotation opacity is the difference between a highlight you can read through and one that obscures the text underneath. It is adjustable in most readers, and the setting lives in a slightly different place in each.

Adobe Acrobat and Reader

Right-click the annotation → Properties → Appearance, where there is an opacity slider. To make it the default for future marks, tick Make Properties Default in the same dialog — otherwise you are adjusting one annotation at a time, which is the usual frustration.

Selecting several annotations first applies the change to all of them at once.

Xodo, Foxit and Okular

All three expose opacity in the annotation's properties or in the toolbar when a markup tool is active. Foxit and Okular both support setting a default; Xodo remembers the last used setting per tool.

Preview on macOS

Preview does not expose an opacity control. Its highlighter uses a fixed translucency. If you need control, the file has to go through another editor.

What opacity actually is

A highlight annotation is a coloured rectangle drawn over the page with a blend mode, usually Multiply, which is what lets the text show through. Opacity scales how strongly it is applied. At 100% with a normal blend mode a highlight becomes opaque and hides the text — which is why a highlight that looked fine in one reader can obliterate the words in another whose blend-mode support differs.

That is also why highlights sometimes print as solid blocks: the printer path may flatten the blend differently from the screen.

If highlights are unreadable when printed

Two fixes. Lower the opacity, which helps in most cases. Or flatten the annotations into the page before printing so what prints is exactly what you saw — the editor can flatten markup, and it is the reliable answer when a document is going to several people whose readers you do not control.

Frequently asked questions

Why does my highlight hide the text? Opacity too high, or a reader that does not apply the Multiply blend mode. Lower it, or use a lighter colour.

Can I change opacity for all annotations at once? Select them all, then adjust properties. In Acrobat, setting Make Properties Default applies it to new marks too.

Why do highlights look different for my colleague? Blend-mode support varies between readers. Flatten before sending if it needs to look identical.

Does opacity affect printing? Yes, and not always the way the screen suggests. Print one page to check before a long run.