That's what DiffRec does. Its a free software that converts your cheap webcam into a spy camera. DiffRec works by recording any changes in movement in the webcam. Here's how to set it up -
1. To use it, install DiffRec and start it.
2. From the 'Select Webcam' menu, choose 'Device 0' (You can choose any item here. Just make sure the webcam starts working). This should start the cam.
3. Click 'Camera Positioned' button, followed by 'Start Detecting Changes' button.
4. Hit the 'Save Differences' button to make DiffRec take photos of any changes it detects.
The recorded photos can then be sorted by time to get them in order.
Tested with Windows Vista on a Dell Inspiron 1545 laptop.
Note: Dotnet Framework 3.5 is required.
Other interesting tools:
F.lux Protects Eyes from Computer Screens during the Night
You cannot print, copy or edit locked pdf files. Pdf files can be protected in two ways: one, a password is required to open a file and two, the file can be opened but you cannot use it for printing, copying etc.
FreeMyPDF can unlock the second type of protected pdf file mentioned above. Just upload your file and get a new file without restrictions. Best of all, no signup is required and its free!
This doesn't work for those files which require a password to open. Since this is a website, it would make sense to avoid uploading confidetial pdf files. Consider a desktop app for that.