“Resizing a PDF” can mean two different things: changing the page size (like converting A4 to US Letter or making a poster smaller) or reducing the file size so it’s easier to email or upload. Here’s how to do both.
Changing page size: the easiest method is printing to PDF. Open the PDF, choose Print, select a PDF printer (“Microsoft Print to PDF” on Windows or “Save as PDF” on Mac), pick the new paper size and choose “Fit” or “Scale to fit.” This creates a new PDF with the content scaled to the new page size. Adobe Acrobat and other editors include tools to change page size directly. On a Mac, Preview’s File > Print dialog offers scale settings too.
Reducing file size: on a Mac, open the PDF in Preview, choose File > Export and select the “Reduce File Size” Quartz filter. Adobe Acrobat has a Compress PDF or Reduce File Size option. Many free tools compress images inside the PDF, which is usually what makes files large.
Tips: keep the original file as a backup, check that text is still readable after compression and choose a moderate compression level for documents with photos. For printing, make sure margins aren’t cut off when scaling. If upload limits are strict, removing unnecessary pages can help too.
Quick tip for How to Resize a PDF: always keep a copy of your original file before converting, compressing or editing, and open the final PDF on a second device to confirm fonts, images and page order came through correctly.
Privacy note for How to Resize a PDF: avoid uploading sensitive documents, like tax forms or IDs, to tools you don’t trust. Built-in apps on your phone or computer handle most PDF tasks without sending your file anywhere.
Learn more about the PDF format on Wikipedia’s PDF article. Find how to reduce file size of PDF, crop a PDF and remove pages guides on Minedit.