We've taken many steps to ensure the Document Portal is fully supported on all web-capable mobile devices. There are only a few differences from the desktop version of the UI, so for most usage it is the same between both. Here are the mobile-specific things:
Button bar
On a phone-sized screen, the button bar runs across the top of the screen instead of down the left side. The file management buttons (Refresh, Delete, Upload, Download) are on the left, and Settings and Close are on the right.
Context menu
On the desktop, you are able to right-click the grid in order to pull up a context menu which lets you do various tasks instead of having to use the buttons on the top/side. On a mobile device, since you don't have a right-click, you can hold a file for about 1 second in order to pop open the context menu. Technically, this works on any touchscreen device.
When you press and hold, the file's row is highlighted and the menu fades in. If we detect that it is a phone-sized screen, the context menu also automatically appears across the bottom of the screen instead of where you touched, for convenience. Options that don't apply to the selected file are grayed out—for example, Preview Selected is grayed out for a file type that can't be previewed, such as a .docx file. Images and PDF files can be previewed. Tap anywhere outside the menu to close it.
Multi-select
On the desktop, you must hold down control/command in order to select multiple files. On a mobile device, multi-select is the default behavior for the grid—you can select and deselect files by tapping them. Each tap on an unselected file adds it to the selection (its row turns blue), and tapping a selected file removes it from the selection.