The Portable Document Format (PDF) is a standard for document exchange that was made by Adobe. Today, many documents are saved as PDF files. However, certain PDF files can be very large if the document contains rich fonts, high-quality images or transparency. Fortunately, Adobe Acrobat allows you to decrease the file size of your PDF files.
Open the PDF file using Adobe Acrobat.
Go to the top menu screen, click "Advanced," then "PDF Optimizer."
Go to the left side of the screen and click "Scanned Pages." You will then have the options to create a "high quality" or "low quality" file. Decreasing the quality will decrease the size of the PDF file. You can also alter the fonts, transparency, and other objects with the PDF optimizer to decrease file size.
Click "OK," after you are done. Next, save the file as the same name to overwrite the old file. Use a different name if you want to keep the old file.