Unlike a word processing file, which allows you to view a document with rules and adjust margins using basic menu tools, a PDF file and its accompanying software often does not. You can determine the margins of PDF files by several ways, two using accompanying software and another by using a piece of reliable hardware.
Print the first page of your PDF document. Use a ruler to measure the space between the edge of the left, right, top and bottom sides of your page and your text or images. The spaces on each side represent the margins of the document.
PDFs were invented by Adobe, so open the PDF document in "sister" programs such as Adobe Photoshop, an image editing program, or Adobe InDesign, a layout program. In Photoshop, each PDF page must be opened separately as an image. Press CTRL + R (or "View" then "Rulers") to display the rulers. You can then use the rulers to determine the distance between the text and edge of the page.
Load the PDF document in Adobe Reader as another way to determine your margins. Click "View" then "Zoom" and finally "Actual Size" from the list of options on the main menu to view the document at full size (100 percent). You can then use your ruler to measure the distance from the edge of the page on screen to the text or images.