We've shown you one way to pin anything to your Windows 7 taskbar, but if you'd rather not install extra software, you can pin a document to your taskbar using Windows' built-in Task Scheduler.
I spent last night looking for a way to pin a specific file in Windows 7 to the taskbar, so that I could open my to do list/scribble pad with a Win+key shortcut. While I only used it to open a specific file in Notepad, it should be able to be used to pin any individual file to the taskbar, rather than pinning to an application on the taskbar. I ended up using an old trick: Task Scheduler.
Essentially, you create a task that opens the file in Task Scheduler, then make a shortcut that points to that task. For example, to open a file named Jot.txt in your Documents folder, open up Task Scheduler, hit Create Task and name it "Jot". If, for your particular task, you need administrator privileges, check the "Run with highest privileges" box. Then it will run as admin without prompting UAC (for those that leave UAC on).
Hit the Actions tab and hit New. Under Action choose Start a program. For, Program/script, browse to the application with which you want to open your file. In this case, C:Windows\system32\notepad.exe. Add the argument Jot.txt (The file you would like to open) and under Start in type C:Users\Shawn\My Documents (the location of the file you want to open).
If you're on a laptop, you'll want to head to the Conditions tab and uncheck both "Stop if computer switches to battery power" and "Start the task only if the computer is on AC power".
Under the Settings tab, make sure "Allow task to be run on demand" is checked. Uncheck any other options that seem distasteful to you. I chose to change the already running rule to start a new instance, because sometimes the task doesnt seem to end when the file is closed.
When you're done, exit out of Task Scheduler and create a new shortcut on the desktop. For its target, type in C:Windows\System32\schtasks.exe /run /tn "Jot", replacing Jot with the name of your task. Pretty your shortcut up with a nifty icon and you're golden! You can pin it right to the taskbar and it will always open the designated file.
That's all it is, but its uses are pretty widespread, since it runs anything as though it was Microsoft's own code. It could also be used to run specific files in a different program from your default for that file type, run things at startup without UAC prompts, or allow non-admin users access to specific admin programs without admin privileges.
Check out the video above for a demonstration of this in action, and share your clever uses for this long-needed feature in the comments.