License Retrieval

I'm currently using a Mac and a Windows PC, but I can't seem to install the app on my Windows laptop. How can I install the app?   

I can't find any information on what versions of macOS are supported - can I use the app on El Capitan?   

I'm planning to stop using my iMac and want to transfer the activation to my new machine. Can I deactivate it myself?    

I think I've lost it

Can I have 3 computers that I work from and would like to be able to access my PDF expert from all 3…is this possible under the one licence?

I bought a PDF Expert license last year, but recently I've got a Mac laptop as my second computer. Can I use my license on both computers?

If I purchase the application for my Mac, can I also use it on my iPhone and iPad without and additional purchase? Or, do I also have to purchase the iOS version separately?

Before I purchase, is it possible to buy one product for using it on all devices (ie. buy for Mac and then use it on iPad and iPhone?)

I purchased PDF Expert for Mac and it's awesome, I am just wondering if I need to get the PDF Expert for my iPad, do I have to purchase again on the App Store?

I've just purchased and downloaded PDF Expert 2 for Mac. When I enter the code it doesn't get activated. Can you provide help?