If your ltd co a/c is overdrawn then you may personally pay into that to clear the deficit. In fact, the bank may already have a personal guarantee from you so that in the event of the company not having the funds, then you may be personally liable. ( check your bank documentation on the overdraft granting to see this )
If you do this, it makes you a creditor of the company, i.e. a loan by a director to the company. However this does not give you any special standing over any other creditors ( if there are any ) and if the company has no way of repaying this then you will be out of pocket. If you propose to liquidate the company then you stand as an unsecured creditor.