When you double-click a PDF file, Adobe Reader opens instead of Adobe Acrobat or Acrobat 3D. Or, Acrobat or Acrobat 3D opens instead of Adobe Reader.
You have Adobe Reader and Adobe Acrobat or Acrobat 3D installed on the same computer.
Note: You can install Acrobat and Adobe Reader on the same computer, but Adobe Technical Support does not recommend this configuration.
When you open a PDF in the browser, an instance of Acrobat or Reader is opened as a process and not as an application. When you close the browser window, the Acrobat or Reader task continues to run for several minutes. When a subsequent PDF is opened outside the browser, the default viewer, either Acrobat or Reader, doesn't start up as expected. End the task so the default viewer can open the PDF.
Adobe Reader and Acrobat both read PDF files. If Adobe Reader is installed before you install Acrobat 7, then Acrobat asks which viewer you would like to be default viewer. However, if you install Adobe Reader on a computer with Acrobat already installed, then Adobe Reader becomes the default viewer. Repairing Acrobat or Adobe Reader changes the default viewer for PDF files in the same manner.
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