A document opening in an unexpected application often needs a file-association change, not a reinstall. The important decision is whether you want to change a single document or every file of that type.

Test the application once

In Finder, Control-click the file, choose Open With and select the application you want to try. Apple also documents opening the application first and using its File, Open command.

Use a copy if you plan to edit a valuable document in unfamiliar software. Check that the app reads the content correctly: page order, images, spreadsheet formulas or other features may matter more than whether a window opens.

If the application cannot read the file, changing its default association will not add support for the format. Check the application's supported formats and the file's origin. Renaming a filename extension is not a reliable way to convert its contents.

Choose the scope deliberately

Once the application is suitable, select the file in Finder and choose File, Get Info. Expand Open With and select the desired app. Apple's instructions identify Change All as the action that applies the choice to all files of that particular type.

Do not click Change All if your intention is limited to this one file. For example, you may want one specialist PDF to use a particular tool while ordinary PDFs continue opening in your usual reader.

Close the document and double-click it again to test the choice. If you changed the whole type, test a second harmless file of that type as well. Confirm that the new default serves both the specialist task and ordinary viewing.

Record the previous application if you are experimenting on a shared Mac. A reversible, narrow change is easier for other users to understand than replacing several default applications at once.

Source: Apple's file-opening and default-app instructions.

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