How to Change a PDF Page Sizeby John Ruiz
PDF files are different from most other common document file types when it comes to editing. Standard PDF reader applications such as Adobe Reader or the Reader app built into Windows 8 can only read PDF files and not edit them. You need a virtual PDF printer or PDF authoring tool to change the page size of a PDF file.
Using a Virtual PDF Printer
Some applications like Adobe Acrobat and goPDF install a virtual printer that you can use to convert a document or image into a PDF file using any application with a Print function. Because you can change the paper size before printing the document, you can alter the page size of a PDF file even without using a PDF editing tool.
Cropping the PDF File
Cropping a PDF file instantly changes the page size of a PDF file. It does not, however, reduce the file size of the PDF file because the cropping function hides the information rather than discarding it. You can crop using Adobe Acrobat by using the Crop function in the Tools sidebar. From there, you draw a box and double-click it to crop the page.