Save buttons, and other document related function are traditionally in the top left corner (not in the extreme, but left aligned with other buttons in a toolbar), and are above the content that it would be saving.
On the web however, many users expect the save button underneath your content, especially if scrolling is involved.
Benefits of Global Save button:
- less intimidating (less cluttered), something to strongly consider -
especially for non techy users.
- more consistent, which improves ease
For global, you may want to add a "Save All" button, and the "Save" button only saves the currently focused item.
If you went with a global save button, it's vital that you have a visual indicator of which document is 'focused' and will be receiving the save command.
This route would also need a keyboard shortcut for saving, to reduce the need to move the mouse so far.
Benefits of individual save buttons
- potentially less confusing (from a which item does this button save standpoint)
- at 1920px wide, it would be much less mousing (however most productivity apps rely on keyboard shortcuts anyway)
If your forms are independent of the other things on the screen (and can appear in a different context at other times in the app cycle), then having it's own save button would make sense. If your forms are directly tied to things outside of the form and only show up in the context of the parent, then a global save button would make more sense.
Since this is a web application, If using individual save buttons, I would recommend you position them on the bottom of the form (like your mockup). If using global, I would position the button above the forms.