A recent update in Smartsheet changed the way we view files. Previously, when you clicked on a file it opened automatically in a new tab and this meant you could have several files open at once and the ability to move between them. The update removed this function and now the file opens in a preview window with little functionality and worse still only view one file at a time.
Please bring back the old way where a pdf (or other) opens in a new tab. Hopefully there are other users out there who will support this functionality returning too.