Many PDFs that are optimized for Web viewing are of a very low resolution, while printouts need to be created with a higher resolution. If you need to change the resolution on your PDF, you must make adjustments to your PDF creation program first and then convert the file to PDF format again. You can use Adobe Acrobat, Photoshop, an Acrobat-integrated program or Adobe's online "Create PDF" tool to complete this task.
Go directly to your Acrobat toolbar if you're using a PDF-integrated Microsoft Office program or another compatible program like InDesign. Select "Preferences" and then "Advanced Settings" or a similar choice, depending on your version. Change the resolution of the PDF to be converted under "File Options."
Go to "Edit > Preferences" in Adobe Acrobat if you would rather do the conversion directly using this program. Then select "Convert to PDF" and find the program that you want to use to convert the PDF (includes InDesign and other popular software options). Select "Edit Settings" and "Standard" under "Adobe PDF Settings" and then "Edit" once more to bring up a screen where you can change the PDF resolution for files that are converted to PDF using the Acrobat program.
Open the PDF file in the program that you used to create it once the new resolution settings are made. Proceed to convert your PDF file at the new resolution (select "Create PDF" in whichever Acrobat-integrated program you used in Steps 1 and 2).
Open your PDF file in Adobe Photoshop if you want to change the resolution, as an alternative to using an Acrobat-integrated program. You will immediately be prompted to select settings for the PDF, including resolution. Type in the desired resolution and proceed to open the file. Save the PDF at the new resolution.
Sign up for an account to use Adobe's Create PDF tool as another alternative to changing the resolution. Select "Convert a File" and load the file that you want to convert into a PDF. Select "Preferences" toward the left side of the screen under "Set Options." Under "Document Options" change the optimization settings to "Print" and then select "Edit Settings" directly to the right. Assure that "Print" (or another viable option, depending on your project) is still selected and then click "Edit." Change the resolution as needed under "General Settings > File Options."
If you are increasing the resolution size, be sure to do a hard-copy printout of the file to assure that it fits your needs. A resolution of 72 dpi is usually acceptable for Web viewing, whereas you need a resolution of at least 300 dpi for a decent printout.