For Uploading Document to Sharepoint Document Library use Following function in Client Object Model:

public void UploadDocument(string siteURL, string documentListName,
string documentListURL, string documentName,

byte[] documentStream)
{

using (ClientContext clientContext = new ClientContext(siteURL))
{        

//Get Document List
List documentsList = clientContext.Web.Lists.GetByTitle(documentListName);

var fileCreationInformation = new FileCreationInformation();
//Assign to content byte[] i.e. documentStream

fileCreationInformation.Content = documentStream;
//Allow owerwrite of document

fileCreationInformation.Overwrite = true;
//Upload URL

fileCreationInformation.Url = siteURL + documentListURL + documentName;
Microsoft.SharePoint.Client.File uploadFile = documentsList.RootFolder.Files.Add(
    fileCreationInformation);

//Update the metadata for a field having name "DocType"
uploadFile.ListItemAllFields["DocType"] = "Favourites";

uploadFile.ListItemAllFields.Update();
clientContext.ExecuteQuery();

}
}

Following link is Also Helpful For you 1) http://blogs.msdn.com/b/sridhara/archive/2010/03/12/uploading-files-using-client-object-model-in-sharepoint-2010.aspx

2)http://msdn.microsoft.com/en-us/library/ee956524.aspx

3)http://www.codeproject.com/Articles/103503/How-to-upload-download-a-document-in-SharePoint-20