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Concatenating new PDFs throws ArgumentOutOfRangeException

I get an exception thrown up from inside obfuscated Aspose code if I try to just create a couple new PDFs and smush them together.
Here’s a 30-line reproduction I ran in LINQPad referencing Aspose.PDF 22.2:

void Main()
	var doc1 = GetErrorPage("testing");
	var doc2 = GetErrorPage("also testing");
	AppendPdf(ref doc1, doc2);	

public Document GetErrorPage(string errorText)
	var doc = new Document();
	var page = doc.Pages.Add();
	var text = new TextFragment($"[Error: {errorText}]");
	return doc;

public void AppendPdf(ref Document ongoingPdfBuildup, Document documentToAppend)
	if (ongoingPdfBuildup == null)
		// this is the first document in this PDF, so just set it directly
		ongoingPdfBuildup = documentToAppend;
		// append the document
		var editor = new PdfFileEditor();
		editor.Concatenate(new[] { documentToAppend }, ongoingPdfBuildup);

Resulting in:

image.png (25.8 KB)

Index was out of range. Must be non-negative and less than the size of the 
collection. (Parameter 'index')
   at Aspose.Pdf.PageCollection.#=zSFF5AGMwLxTiLE$pRSQCiZs=(Int32 #=zvLH6zsk=)
   at Aspose.Pdf.PageCollection.#=zfIDpZtA=(Int32 #=zvLH6zsk=)
   at Aspose.Pdf.Document.ProcessParagraphs()
   at Aspose.Pdf.Document.#=zG7VhpvNMzChd(Stream #=z4_mitY8=, SaveOptions 
   at Aspose.Pdf.Document.#=zQg2rMssyUtgB(String #=zYiXckzBWQh06)
   at Aspose.Pdf.Document.Save(String outputFileName)

There’s nothing wrong with the output of GetErrorPage; if I just call Save, the resulting file works and looks like I’d expect.

It also works if I append one of these to a PDF created in some other way (my actual code only experiences this if the first one of the documents being concatenated is missing, otherwise it seems to be fine). So I think there’s something in PageCollection that isn’t getting properly set by Pages.Add()?


We have managed to reproduce the same issue at our side. For the sake of correction, we have logged this problem in our issue tracking system as PDFNET-51491. You will be notified via this forum thread once this issue is resolved.

We apologize for your inconvenience.

1 Like

Addendum to this:

(my actual code only experiences this if the first one of the documents being concatenated is missing, otherwise it seems to be fine)

Actually that’s not correct; if they’re being concatenated to an existing document, nothing crashes and the pages insert fine, but there’s no content on them, it’s just a blank page. Since that’s not the case if these generated pages are saved instead of concatenated, I suspect this might be related.


We have logged this detail in our issue tracking system. We will be sure to inform you via this forum thread once there is an update available on it.