You can read a report PDF as a stream simply by making a HTTP request to SSRS. Something like this:
string URL = "http://host/path/Pages/ReportViewer.aspx?%2freports%2fCustomReports%2fReportName&rs:Command=Render&rs:Format=PDF&OrderNum=" + row.OrderNum;
System.Net.HttpWebRequest Req = (System.Net.HttpWebRequest)System.Net.WebRequest.Create(URL);
Req.Credentials = System.Net.CredentialCache.DefaultCredentials;
Req.Method = "GET";
System.Net.WebResponse objResponse = Req.GetResponse();
The problem is, most of the stock SSRS reports are designed to take the GUID of a report dataset as their only parameter, not domain values like an OrderNum or InvoiceNum. I’d like to know how you
Ask Epicor to Generate an invoice for that invoice number
If the report style is set to output to database rather than XML, running the report should result in a GUID being generated and a set of tables with that GUID in their names being created in the EpicorEnvironmentName.Reports database (e.g., Live.Reports). But I’m not sure how you’d obtain that GUID to pass it to SSRS.