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