Open the PDF file you wish to reduce in Adobe Acrobat. This is not an option in the free version of Adobe Acrobat (which is Acrobat Reader).
From the File menu hover your cursor over “Save As Other…”, which will open a new submenu. Select “Reduced Size PDF”.
Select what versions of Acrobat you want the PDF to compatible with. Choosing newer versions will result in smaller file sizes, but will render the file un-openable in older versions of Acrobat.
Using the Adobe Acrobat “PDF Optimizer” Command
PDF Optimizer provides finer control for reducing the size of PDF files. For most users, the default settings will provide the best reduction in file size. Optimizer saves space by removing embedded and duplicate fonts, compressing images, and removing items from the file that are no longer needed.
From the File menu hover your cursor over “Save As Other…”, which will open a new submenu. Select “Optimized PDF…”.
Click the “Audit space usage” button to see a breakdown of what is taking up space in your PDF file. This will allow you to see if your images are making the file too big, or if your embedded fonts are inflating the size. Each aspect of your PDF will be rated by bytes and percentage of total size.
Adjust your settings. Leave as default, or fine-tune your settings as needed. You can switch to different aspects of your PDF (Images, Font, Transparency, etc.) by using the menu on the left side of the window. You can choose to not optimize specific aspects by unchecking the boxes next to each menu item. This can be useful if you want to optimize the text but leave the images unaltered.
When optimizing images, you can change color images to grayscale, compress, downsample, and lower the quality. Compression of images can result in poor quality that is not suitable for printed materials. Always check the quality of your optimization before committing to saving the changes.
When optimizing fonts, unembed fonts that you know all of your readers will have. For example, if you are sending the PDF to people at your school, they most likely will all be using the same system to read it, so those fonts do not need to be embedded.
Press OK. Your PDF will be converted using the new settings. You can check the new size by saving the file or by opening the PDF Optimizer again and clicking “Audit space usage” button.