When you add a pdf file as a resource, there are three options

1. New window: This opens the pdf document in a new window that is separate from your current Moodle window. The window contains a frame in which the pdf document is displayed. That frame has its own scroll bars that are separate from the browser’s scroll bars. If you increase the magnification of the pdf document, the frame size will not change so that the right edge of the pdf document might be cut off. To scroll horizontally, you must first scroll down in the browser window, then use the frame’s horizontal scroll bar, then scroll the browser window back up. Not very efficient.

The effect of “new window” depends on the browser:

Internet Explorer 7– opens in a new tab rather than a new window
Firefox 3– opens in a new window
Chrome 2 – opens in a new tab rather than a new window
Safari 4 – opens in a new window
Opera 9 – opens in a new tab and then resizes the entire browser window to the width and height set by Moodle.
Safari 3 (Mac) – says this operation is not allowed. Upgrade to Acrobat Reader 9.1

Moodle will set a “default window” size for the new window. This is usually too small so the user will have to maximize the window. If you erase the numbers in those two boxes and leave them blank, the new window appears to open maximized, except in the case of Safari which opens a really tiny new window when no sizes are specified in the Moodle setup.

You can force Firefox to open all new windows in a new tab instead by typing about:config in the url bar and setting the following properties:
1. ‘browser.link.open_external’ should be 3
2. ‘browser.link.open_newwindow’ should be 3
3. ‘browser.link.open_newwindow.restriction’ should be 0 (the normal setting is 2)
Note: The Firefox help file claims that setting the tab option to “open a new window in a new tab instead” will do exactly that. It doesn’t in Moodle. That is probably because Moodle is trying to specify that the new window should have a certain size and doing this forces Firefox to ignore its tab option setting, even if you leave the size settings blank in Moodle.
2. Same window: This replaces the current page with a new page showing the pdf document in a frame as described above. You are still within the Moodle system, however, with the Moodle navigational breadcrumbs still visible. The user will need to use the back button or the breadcrumbs to navigate back to the course page. Safari users on Mac also need to upgrade to Acrobat Reader 9.1

3. Force download: You must first choose “Same window” and then check this box. The pdf document will be opened in a new window that is outside of the Moodle system. The document will be displayed at the largest magnification that fits the window rather than appearing inside a Moodle frame as with the “new window” choice.

NOTE: There is a problem with displaying pdf documents using “new window” or “same window” with Moodle 1.9.4, Firefox for Windows, and older versions of Adobe Acrobat Reader. Rather than displaying the pdf document, the user will see a blank window except for a link that says “direct link to this file”. The user would then need to click on this link to load the pdf document. The problem disappears after upgrading to Acrobat Reader 9.1.

NOTE: Firefox for the Macintosh does not have an Adobe Reader plug-in like the version for Windows. Thus users on a Mac will be asked to download a pdf document which they would then have to open in Acrobat Reader or Preview.

There are two add-ons that I know of that allows one to view pdf documents within a browser in Firefox for the Mac. One is “Firefox PDF Plugin for Mac OX X 1.1”. This extension will crash Firefox, however, when trying to view a pdf document that has been setup to use “new window” or “same window”. It will display a pdf document using “force download”. The other add-on is Shubert’s “PDF Browser Plugin 2.2.2”. This one will display a pdf document using any of the three possible methods.