Why are different PDF compression ratios different? Firstly, it depends on the number of dpi sets, secondly, the proportion and structure of images and texts in PDF files will also have some influence, and finally, the strength of compression tools.

Let's give a simple example, such as this PDF online editing platform: PDF365. Free PDF compression on this platform is to minimize PDF files while ensuring the same picture and text quality.

I am satisfied with the compression quality of my PDF documents, almost all of which are pictures, and the pictures are not distorted.

So it is also important to choose a good compression tool. The above is my personal opinion on different compression ratios of PDF.