preview pdf files in the left pane and support for "Download latest" functionality for pdf's

You could tap-and-hold the file and choose "Open" to open the file in the editor instead of opening a preview. Then you can select "Download Latest".

Thanks, Alexander!  However, you have to admit that this workaround is rather inconvenient because I have to confirm on several occasions that I really, really want to open a binary file, and then I have to look at meaningless mumbo-jumbo. I would find it much more convenient if Textastic didn't ask for a confirmation and simply displayed "No preview available" in the right pane.

Even better: why not provide "Download latest" in the context menu that appears when I tap-and-hold a file name? This is a minor change that would make our lives much easier!  Thanks!

Yes, that would be a better solution than the workaround I mentioned.