You can reduce the size of a PDF file using a PDF editor. To compress a PDF using Adobe Acrobat:
Open the tool, “Optimize PDF,” from the Tools menu.
Select Open from the drop-down menu, then choose the file to be edited.
Select Reduce File Size from the top menu.
In the dialog box, choose the file version compatibility option, such as Retain Existing or a different listed file format.
Rename and save the file using the Save As dialog box. You can keep the same name and overwrite the original PDF file or you can choose a new name and safe a new PDF document.