The PDF (Portable Document Format) is quite sophisticated in the way it creates documents. Therefore, PDF files can end up being pretty large. If you need to reduce the size of a PDF for Emailing or other purposes, you can use the MacOS included Preview App.
Preview Reduce Size
If you do not have a third party App to handle PDF’s or an App that reduces the size of files, you can use the Preview App built in to the macOS. Here is a PDF of a plan to build a bookcase:
It contains lots of pictures so the file is quite large at 28 MB. If you wish to reduce the size of a PDF file like this one, just open it in the Preview App and select File → Export:
Do not choose Export as PDF, but just the plain Export command. You will be taken to a window like this:
There are two things you need to do here. First, click on the Quartz Filter and select “Reduce File Size”. Then, before you save the file, change the file name. After the file is saved open it and check the file size:
Check out the huge savings in size here. The same file that was 28 MB is now about 765 KB! That is pretty amazing.
There is a caveat here though. If the file you are working with has a lot of images, they will take a good hit in quality. They will not look as good as the original. Text seems to be unaffected. If you need not have the images look pristine, then using this method makes sense.
I did some tests on PDF documents that were primarily text based. The size reduction is still quite significant here also.
If you don’t have a third party PDF App, you can always use the built in Preview App to reduce PDF file size. It works quite well and is very fast.