No there are no limit of issuing the character certificate. One can obviously get the character certificate from the competent authority if he/she loses it. Firstly, you should file a complaint in your nearest Police Station about the lose of your document. After that take the receipt as given by the PS to the authority from where you have issued the character certificate (mainly your school) and they will guide you out about the subsequent procedures in order to get the same.

I hope this answer helps. All the very best for your future endeavors!