In order to find out how to make a file size smaller of the file, first, get rid of everything that is unnecessary, like double images, unneeded pages, or inserted attachments. Then you can reduce the rest of the content by applying file compression tools. Usually, images occupy most of the space, so reducing their size may help you to save some extra space. In case of a PDF file, optimization can also reduce the size. It is necessary to have a backup copy of the file to be able to restore it.