some journey into PDF and duplex-scanning

[kapper.net, inc.]

Hi,
this story starts with a HP6830 AIO printer that does not duplex scanning, nor does its driver packages proper TWAIN-driver-setups on Windows 10 (I virtually tried every way), but it installs a WIA driver, therefore NAPS2 can handle it, although it can not propperly handle the ADF (scans first page then reports the scanner is busy while all other pages are fed through the scanengine), finally I got my hand on the Win10 App HP Scan and Capture, at least ADF document scanning does work using this one, saving those pages to a PDF works too and I planned to put this PDF into NAPS2 for its magical page-reordering, but NAPS2 fails opening this PDF with this statement:
2018-01-15 08:11:07.8580 Error importing PDF file. System.NullReferenceException: Der Objektverweis wurde nicht auf eine Objektinstanz festgelegt.
bei PdfSharp.Pdf.PdfPages.GetKids(PdfReference iref, InheritedValues values, PdfDictionary parent)
bei PdfSharp.Pdf.PdfPages.FlattenPageTree()
bei PdfSharp.Pdf.Advanced.PdfCatalog.get_Pages()
bei PdfSharp.Pdf.PdfDocument.get_Pages()
bei NAPS2.ImportExport.Pdf.PdfSharpImporter.Import(String filePath, Func`3 progressCallback)

therefore I opened the first PDF in irfanview and printed this one through bullzip-pdf-printer and finally this PDF could be opened (though some quality loss) and pages could be reordered.

great tool, though I'd love to have the HP6830 be commanded correctly for page-scanning :)

regards
hk

[Ben Olden-Cooligan]

Can you attach a sample PDF that has this issue?