Api reference or SDK for web Application

I used your service and it really is helpful for my desktop system. I can create, edit my documents easily anytime.
I am running a web application where users can upload files (word,excel,ppt).
But they can not view/edit these files online in my platform. To view or edit the users need to first download the files and then again need to upload these. So I want them to get free from the download and upload again cycle. I need some service through which the user just click on file and can view/edit the file.
Is there some API or SDK service from your company by which I can accomplish my target. If any kindly also provide the billing information of this.
Thanks.

Look at CODE (Collabora Online Developer Edition) which is created specifically for this purpose.

Thanks for the response.