Open command (File menu).

Use this command to open a PDF or Text document in a new window. You can have more than one document open at a time. Use document tabs to switch among the multiple open documents. See Document tabs.

Supported documents are those in PDF or ASCII/Unicode (Text) formats. Use "Files of type:" combo box to choose between the various formats, or all of them.

Keys: CTRL + O (,), COMMAND + O ()
File Open dialog box