how do i reduce KB size of pdf on my mac

If you are using Apple's Pages application, there is a File menu : Reduce File Size… before you export it to PDF. The more you put into a document the larger the PDF will become too, so maybe you want to review what you can omit before PDF generation.

All of these reduction efforts will have an adverse effect on the sharpness of the final PDF content, and even if you manage to get the PDF below 300 KB, it may look dreadful to the person opening it. Do check it before passing it on.

From the spotlight search ( command spacebar ) > ColorSync Utility.app

>Create generic PDF you can try this filter.

Once you launch the app, drag and drop your PDF on the icon in the Dock.

and save.

You can also use the Reduce File Size Filter.

Open the PDF document in Preview. From the Preview menu select Export. From the resultant Menu, select Quartz Filter to Reduce File Size. You may need to do the process more than once to progressively shrink the file size