Set a Different App to Open PDFs Automatically

When you double-click a PDF on your Mac, it opens in whatever app your system has set as the default — usually Preview or Adobe Acrobat Reader. You can change this so PDFs open in a different program instead. The process takes less than a minute and works the same way whether you want to switch to Chrome, Firefox, a different PDF reader, or any other app on your computer.

The change applies to all PDFs you open by double-clicking them. It does not affect PDFs you open by right-clicking and choosing a specific app, and it does not change which app opens PDFs that are attached to emails or embedded in web pages — those follow their own rules.

Key Takeaways

  • Right-click any PDF file, select "Open With", and choose the app you want, then click "Change All" to make it the default for all PDFs.
  • You can also change the default through System Settings by finding the PDF file type and selecting a new app from the dropdown.
  • Different apps can handle PDFs differently — some are faster, some let you annotate, and some work better offline.
  • Your choice only affects PDFs you open from your Mac itself; email clients and web browsers may still open PDFs in their own viewers.
  • You can switch back to Preview or any other app at any time using the same method.

Change the Default Using Right-Click and Open With

Find any PDF file on your Mac — it can be anywhere: your Downloads folder, Desktop, Documents, or inside an email. Right-click the file (or hold Control and click if you have a single-button mouse). A menu appears with several options.

Look for "Open With" in that menu. Hover your cursor over it and a submenu slides out showing all the apps on your Mac that can open PDFs. You will see Preview at the top, followed by other options like Adobe Acrobat Reader, Chrome, Firefox, or any other PDF-capable app you have installed. Click the app you want to use.

The PDF opens in that app. Now comes the important step: close the PDF and right-click the same file again. Go to "Open With" again and look for an option that says "Change All" or "Always Open With" — the exact wording depends on your macOS version, but the button will be near the bottom of the submenu. Click it. From now on, all PDFs on your Mac will open in the app you chose.

Change the Default Through System Settings

If the right-click method does not work or you prefer a more direct route, you can change the default through your Mac's System Settings. Click the Apple menu in the top-left corner of your screen, then select "System Settings" (or "System Preferences" on older Macs).

In System Settings, look for "General" in the sidebar on the left. Click it, then scroll down until you see a section labeled "Default apps" or "File associations". You may need to scroll quite a bit depending on your macOS version. Once you find it, look for "PDF" in the list of file types.

Click the dropdown menu next to PDF. A list of all apps that can open PDFs appears. Select the app you want to use as your default. The change takes effect when ready. Close System Settings and the next time you double-click a PDF, it will open in your new default app.

Why You Might Want to Change Your Default PDF Viewer

Preview, which comes built into every Mac, is fast and lightweight. It opens PDFs almost when ready and uses very little memory, which matters if your Mac is older or you have limited storage. But Preview has limited features — you cannot easily add comments, fill forms, or search across multiple PDFs at once.

Adobe Acrobat Reader is more powerful. It lets you annotate PDFs, fill out forms, and sign documents. The tradeoff is that it takes longer to open and uses more of your Mac's resources. Chrome and Firefox are useful if you work with PDFs in web-based tools or want to use browser extensions to manage them. Some people prefer third-party readers like PDF informed or Skim because they offer a middle ground between speed and features.

Your choice depends on what you do with PDFs most often. If you mostly read them, Preview is fine. If you fill out forms or mark them up regularly, a more full-featured app saves you time.

What Happens to PDFs in Email and Web Browsers

Changing your default PDF viewer affects only PDFs you open directly from your Mac's file system — when you double-click a file in Finder or on your Desktop. It does not change how PDFs behave in other contexts.

If you click a PDF link in a web browser like Safari or Chrome, the browser usually opens it in its own built-in viewer, not your default app. You can override this by right-clicking the link and selecting "read Linked File", then opening the downloaded PDF from your Downloads folder — that will use your default viewer.

PDFs attached to emails in Mail, Gmail, or Outlook also follow their own rules. Mail uses Preview by default. Gmail and Outlook open PDFs in their web viewers. If you want to open an email attachment in your default app, read it first, then open it from your Downloads folder.

Switch Back to Preview or Change to a Different App

You can change your default PDF viewer as many times as you want. If you decide you prefer Preview again, or you want to try a different app, use the same right-click method or System Settings route. There is no limit to how many times you can switch.

Some people keep multiple PDF apps installed and switch between them depending on the task — Preview for quick reading, Adobe for forms, and a web browser for PDFs they want to share or collaborate on. You can also set different defaults for different file types if your Mac supports it, though PDF is the most common one people change.

Frequently Asked Questions

Will changing my default PDF viewer affect PDFs I have already opened?

No. PDFs that are already open in Preview or another app stay in that app. The change only affects PDFs you open from now on. If you want to open an old PDF in your new default app, right-click it and choose "Open With" and select the app you want.

Can I set different default apps for different types of PDFs?

macOS does not let you set different defaults based on the PDF's content or size. You can only set one default app for all PDFs. However, you can always right-click any PDF and choose a different app to open it just that one time.

What if the app I want does not appear in the "Open With" menu?

The app may not be installed, or macOS may not recognize it as a PDF-capable app. Try installing the app again or checking its documentation to confirm it supports PDFs. If it still does not appear, you can usually drag and drop a PDF onto the app's icon in the Dock or Applications folder to open it.

Does changing my default PDF viewer slow down my Mac?

It depends on which app you choose. Preview is the fastest option and uses the least memory. Adobe Acrobat Reader and some third-party apps use more resources. If your Mac is running slowly, switching back to Preview may help, especially if you open PDFs frequently.

Can I undo the change and go back to what I had before?

Yes. Use the same right-click or System Settings method to switch to any other app, including Preview. There is no permanent change — you can switch back and forth as many times as you need.