Which activity requires the PDF file to be opened with Acrobat Reader to read it?

The activity that requires the PDF file to be opened with Acrobat Reader to read it is the option of extracting text directly from the PDF. This is because the "Get Text" activity typically relies on the underlying text layer of the PDF which is managed by Acrobat Reader for optimal access. It processes how text is stored and displayed in the PDF format and allows for accurate extraction.

In contrast, some other activities like reading PDFs with OCR or extracting PDF data may utilize different methods or tools that either convert the PDF to images first or retrieve structured data from the underlying file. These methods do not necessarily mandate the use of Acrobat Reader, as they can work with other formats or applications that handle PDF content in alternative ways. Therefore, "Get Text" is specifically tied to Acrobat Reader's capability to present and manage the PDF's text layer effectively, making it necessary for that activity.