Check if PDF is complete

Im creating a PDF from crystal reports and then open it with adobe reader straight after.

However, sometimes I think adobe reader tries to open the file before it is fully created. (The pdf file exists but maybe still not complete ??)

Here is my code:

rep.ExportToDisk(CrystalDecisions.Shared.ExportFormatType.PortableDocFormat, Utilities.Paths.pathToPDFs + fileNamePreFix + dt + ".pdf");

Open("\"" + Utilities.Paths.pathToPDFs, fileNamePreFix + dt + ".pdf" + "\"", Utilities.Paths.pathToAdobeReader);

System.Diagnostics.Process.Start(Utilities.Paths.pathToAdobeReader, "\"" + Utilities.Paths.pathToPDFs + fileNamePreFix + dt + ".pdf" + "\"");

Could it be that the ExportToDisk is returning early before the PDF file has been fully created ?

This is the error message I am getting:

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Clik here to view.

Once I click OK, then then Adobe reader displays the report.

J