In order to achieve compression, the best way to do so is to obtain a compression software. There are little tricks you can do here and there to decrease the file size but that is nothing compared to the amount of compression you will get when you use software. It utilizes complex algorithms to get the size of the file as small as possible. Even being able to reduce the file by half its size is crucial especially in a time sensitive situation.
When you compress, not only are you trying to save space on your computer but you are also trying to avoid potentially problematic situations. A great example of a scenario where compression is critical is if you tried to send a PDF by attaching the file to an email. Most email servers have limits as to how big an attachment file can be and this is a serious problem when you try to send a file that exceeds the allotted size to an important client. With compression, this would not be a problem at all.
Free Compression Software
A lot of different websites offer free compression software for people to use, however, they are usually not very good, most of them anyways. In my experiences of trying out different free trials, CVISION Technologies is one of the few that offers their product for people to use and test out. Also, their free compression software is one of the best I have seen for awhile. To try it for free, you can click on the download button at the top. If you still have questions or doubts, feel free to contact CVISION directly.