Offer zooming in and out with touch screen pinch and stretch actions.

The documentation has never been available under a free software license and doesn't offer the right to make derivatives of it. Documentation is copyrighted just like code. Linking to the CopperheadOS technical overview is also misleading now that it offers more features and improved sandboxing compared to what it did before it was relicensed.

Please, add a GET IT on F-Droid badge with link in the README.md file

Very excited to see a FOSS pdf-viewer app finally it F-Droid, so thank you! However when trying to install from the F-Droid app is impossible, as there is no download link and the app itself is greyed out in the apk list.

Manually downloading the apk from https://f-droid.org/repository/browse/?fdid=org.ninthfloor.copperpdf wasn't helpful either, as when trying to install and error with message "There was a problem parsing this package" gets thrown:

I am using am SM-N910H smartphone. It is rather fast system to operate with even large books in pdf format. But this app opened and rendering every new page really slow.

The app supports min SDK 23, which is incompatible with some of the popular Android devices currently in use such as Galaxy J2, J1 Ace, Grand Prime, and Oppo A37f. These Android devices support min SDK 22.

Borrowing the "Copper" prefix by CopperheadOS makes this appear to be even more associated with CopperheadOS than the original PDF application. CopperheadOS has been filed as a trademark and that could easily be considered infringement. It's clearly based on the CopperheadOS brand since this was forked from our code while not being tied to the project.

https://en.wikipedia.org/wiki/Confusing_similarity