You will need Adobe Illustrator for this. Now, don't panic if you're not familiar with Adobe Illustrator, all you gotta do is go to File - New and create a new document. Select the size you need and click OK. Since it's blank, all you have to do now is to save it as a pdf, under File - Save As. The drop-down menu will allow you to select pdf.
By the way, if you're wondering why this isn't part of Adobe Acrobat, it's because Acrobat is a program for sharing, not a page layout program, not even Acrobat Pro. If you want to do page layout, you need a vector program, like Adobe Illustrator.