To select a listed PDF file, click it.
To select all the PDF files listed, click Select All.
To add noncontiguous PDF files to or remove them from the selection, Ctrl-click/Command-click them.
To add contiguous PDF files to the selection, Shift-click.
To open, print, or email the PDF files, use the buttons above the files pane.
To start combining PDF files into a single PDF file, click the Combine Files button and follow the instructions in the wizard.
To start a review, select the PDF and choose Send For Review > Distribute For Shared Review or Send For Review > Send By Email For Review.