Changing document name / file name to memory-stream generated pdf

Hi, I am splitting a document into several documents using
PdfFileEditor pdfEditor = new PdfFileEditor();
MemoryStream[] outBuffer = pdfEditor.SplitToBulks(document.Data, numberOfPages);
This ends up into another service so everything is managed in memory…

And everything works finely…
But then, opening the document is opened in the UI and the name is like a Hexadecimal or some XML section… Is there a way to set the document name when splitting (or merging)?
Or otherwise, how can I do that without saving the pdf to a file? I am only processing it and seems that all the name-setting capabilities depend on having a filesystem…

@joslat

Are you sending the PDF file to the browser for download? How it is being opened in the UI through your application? Can you please share the complete code snippet?