Is there a feature that allows an admin to approve or sign a document digitally?

Thanks for reaching out to us here, Khaled3.

If you need to add a digital signature to your transactions, you can scan and add them into QuickBooks Desktop. To begin, write your signature on a piece of paper. Next, scan the image to your computer at an 11:3 aspect ratio, and we'll size your signature then place it above the signature line on Intuit supplied checks. Finally, save the image in .bmp, .jpeg, .png, or .tiff format.

Once done, you can follow these steps to add and use the electronic signature:

1. Go to File > Printer Setup.
2. Select Check/Paycheck from the Form Name drop-down list.
3. Click the Signature button.
4. Hit the File button and find the file that contains the signature image, then select Open.
5. Press OK in the Signature window, then select OK in the Printer Setup window.

Please see this sample screenshot for a visual guide:

If you encounter an error message, you can follow the steps in this article to fix it: Resolve error 15XXX when downloading QuickBooks Desktop updates, To view other guides and tutorials, feel free to visit our general help topics page. 

On the other hand, use a third-party app for the digital signature, You can find the applications here: Apps for QuickBooks Desktop.

I'm just a post away if you have any follow-up questions. You can click the Reply button and I'll get back to you as soon as possible. Take care!