1. Please save the document first.

2. Click the "Office Button" again.

3. Select the "Prepare-Add Digital Signature" option.

4. Click OK.

5. In the "Get Digital ID" window that pops up, select "Create your own digital ID".

6. Enter your own information in the Create Digital ID window.

7. In the next window, enter the purpose of adding the digital signature.

8. Finally, click OK.

Second, how does the macbook enter the bios?

1. The following startup key combinations can be used on Intel-based Mac computers.

2. Hold down the C key when starting-start from a bootable CD or DVD, such as the included Mac OS X installation CD.

3. Hold down the D key when starting-If DVD 1 is inserted and installed, it will start as Apple Hardware Test (AHT).

4. Press and hold the Option-Command-P-R key until you hear two beeps-press and hold the Option key when resetting NVRAM startup-and start to enter the startup manager. You can choose to start with the Mac OS X volume. Note: Hold down the N key to display the first bootable network volume.