You don’t open PDFs, you place them.
I'm new to using InDesign CC. How do I place a PDF file in InDesign CC.
File > place
I was able to place the PDF file, but it only placed the first page.
When go to the "Place" menu, at the lower left, there is a check box for "Show Import Options". Check this box, and then when you select your PDF, you'll be met with a dialog which allows you to choose the pages you want to import. Hope this helps.