Here are some of the links that will help you download PDF versions of Bhagwad Gita and other scriptures that you are looking for. I hope you would be benefited by these links:
Download Bhagwad Gita Hindi PDF
Download Vishnu Sahasranama in PDF
Download Hanuman Chalisa in PDF
Download Sri Durga Saptashati
If you know any other destination that provides PDF downloadable version of any of these documents, please share through comments as it will help the readers greatly.