Is your PDF too large to upload on a form? Here, pages are turned into images and the size is reduced based on the quality you choose. Your file never leaves your device.
Select High Compression. If it is still too large, first Split the PDF and keep only the pages you need.
No — compression happens in your browser, there is no server.
With this method, every page becomes an image, so text cannot be selected. It is still perfectly fine for reading and printing.
If the PDF was already text-based and light, turning it into images does not reduce the size — it can even increase it. Such a PDF does not need compression at all.