Adobe Reader

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To change the default application for opening .pdf files to Adobe Reader:

Method One Windows 10:

1. Right click on the .pdf file
2. Click on Open with
3. Click on Choose another app
4. Click on Adobe Reader 

5. Check the Always use this app to open .pdf files box

Method Two Windows 10:

1. Click on the Start menu button. This is the Windows logo in the bottom left corner of the screen on the taskbar.
2. Click on Settings. This is the gear-looking icon
3. Click on Apps
4. Click on Default apps. This is on the left side navigation pane.
5. Scroll down to Choose default apps by file type and click on it
6. All file types recognized by your machine are listed in alphabetical order. Scroll down to .pdf
7. Click on the app icon shown or the + button if no app icon is shown
8. From the pop-up menu choose Adobe Reader

Mac OS:

1. Open up Finder, navigate to the file in question and right-click it to bring up the contextual menu
2. Select Get Info and then from the box that appears you'll find, about halfway down, the heading Open with:
3. Click this and you'll see the default app currently associated with .pdf's.
4. Click on the dropdown menu, select Adobe Reader, then click the Change All button