Is it possible to edit and format Google documents(word, text-file, excel, PPT, PDF) using Google Docs API.
All i could do so far create, download, upload, delete file and replace with with another one. i want for example if user hit bold button then i could use a class in Google Docs API to format the text to be bold.
You are correct, you cannot edit the content using the Google Documents List API. You can edit spreadsheets using the Google Spreadsheet API, and for scripts to run inside Google Docs, you can use Google Apps Script.