We are trying to load test Cognos 7 impromptu reports published to Upfront but LR is not able to record the browser activity while the report is in 'running' state. How do we capture this wait time and let LR record the PDF output..
Typically applications such as this will have a refresh interval associated with the "running page," dropping out of the constant display of the update page when results are available. You simply need to implement this re-request structure in your script, dropping out when you receive a page back which does not have the status update of "running"
As to the PDF, since you are using HTTP for your transport it will download over HTTP just fine.