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
http://www.gitapress.org/BOOKS/GITA/18/18_Gita.pdf
Download Vishnu Sahasranama in PDF
http://www.gitapress.org/BOOKS/226/Sri%20Vishnusahasranaamsatrotam.pdf
Download Hanuman Chalisa in PDF
http://www.gitapress.org/BOOKS/1378/1378%20Sunderkand%20&%20Hanuman%20Chalisa.pdf
Download Sri Durga Saptashati
http://www.gitapress.org/BOOKS/paath/118/Durga_Saptashati.pdf
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.
