有關公司文件的簽署~

If the document is clearly spelled out that the said document should be signed by a director and the company secretary, a director, even also acting as the company secretary, could not sign on it. The director could only act himself in one capacity.
But, I think not all documents must be singed by a director and the company secretary. Sometimes, the doucments could be signed by 2 or 1 director(s) depneding on its nature. Please check with the requirement of the other party.