The file icons for PDF files on your PC have seemingly received a change with the latest versions of Google Chrome. The old file icon, which was simply the Google Chrome four-colour circle logo ...

To properly sign a PDF on your Android phone or tablet, you'll need to download an app from the Google Play Store.

You can use the macOS Finder's Copy command to copy and paste files. But here's how to use the same command to copy file icons into Preview.