The optimal strategy on how to minimize file size will vary depending on whether you are dealing with a PDF, an image, a spreadsheet, a video, or a regular document. The first step will be getting rid of all the unnecessary material and then applying compression according to the type of file. Reducing overly large images and selecting good formats will go a long way towards decreasing the amount of storage needed. There are also compression methods for PDFs and office documents that might come in handy.
