I hope you meant to say that you are *planning* to transition your company to electronic signature for approval etc.
In any event, ISO standards require that you indicate the original author of the document on all releases of the document, and that you indicate the initial release of the document with a revision character that must not be blank (i.e. "A" or "01" or "0" or "-" but not blank or space as in " " ).
21 CFR Part 11 requires that all releases (including your initial release) capture the approver(s) and date of approval. This information must be tracable to the document -- you may put it in the revision block, the title block, or reference an ECO number which contains the signature information.
There are also other requirements that you should clearly understand before implementing any procedure changes with regard to electronic signature -- for example, each approver (system user) must sign a paper document indicating that their electronic signature is legally equivalent to their handwritten signature.
Something that you mentioned that might be of concern is that "...the signatures are typed on the drawings". How are you validating that the typed signatures are applied by the actual person? The application of these signatures should be password protected and should be electronically secure (not modifiable) within the document.
Implementing electron signature is not difficult if you understand the requirements -- which are mostly very logical. I hope this helps you.