Please make sure:
-> Since you are receiving PDF, you will either need to use passthru pipeline which simply publish your message to the messagebox database. Or write your custom pipeline if you are dealing further with PDF file.
-> The error is mentioning clearly that your received message is suspended because there is no subscriber who is waiting for that message. Note that the basic fundamental of BizTalk is to receive message, process it(if any), and send to the destination since it is an integration tool. Here, you are not sending your received message to anybody so your message is suspended and is in messagebox. The one way to get rid of this message is to create a subscriber for that message. Subscription can be created using Send Port filter, Orchestration Receive Port etc.
-> If your concern is only about name of the file, you can use FILE.ReceiveFileName property but to get this inside orchestration, you can't directly use passthru pipeline because your XLANG Engine deals with xml message only. So unless you have a xml message you can't read this inside orchestration.
Now, coming to your scenario, If you are not dealing with PDF at all, you can simply ignore the file in your custom pipeline once you read the filename, and wrap it inside a new xml message and publish this to the messagebox so that your orchestration can subscribe that message and insert entry into the SQL database using SQL adapter.
In case you need that message further, then you can wrap binary content of PDF inside new xml element along with file name in Custom Receive pipeline. In this case you will need to use convert byte array to Base64String using a method like Convert.ToBase64String(byteArray). On send pipeline, again convert Base64String to byte array and write it into the file (i.e. PDF file). Considering the performance, it is not good to publish entire file into messagebox if your filesize is large.
I am not sure if you are doing anything with received PDF file. So if could give me the details what you are doing further with the pdf I can recommend you the exact solution.