c# - itextsharp trimming pdf document's pages

Question

I have a pdf document that has form fields that I'm filling out programatically with c#. Depending on three conditions, I need to trim (delete) some of the pages from that document.

Is that possible to do?

for condition 1: I need to keep pages 1-4 but delete pages 5 and 6

for condition 2: I need to keep pages 1-4 but delete 5 and keep 6

for condition 3: I need to keep pages 1-5 but delete 6

Answer 1

Use PdfReader.SelectPages() combined with PdfStamper. The code below uses iTextSharp 5.5.1.

public void SelectPages(string inputPdf, string pageSelection, string outputPdf)
{
    using (PdfReader reader = new PdfReader(inputPdf))
    {
        reader.SelectPages(pageSelection);

        using (PdfStamper stamper = new PdfStamper(reader, File.Create(outputPdf)))
        {
            stamper.Close();
        }
    }
}

Then you call this method with the correct page selection for each condition.

Condition 1:

SelectPages(inputPdf, "1-4", outputPdf);

Condition 2:

SelectPages(inputPdf, "1-4,6", outputPdf);

or

SelectPages(inputPdf, "1-6,!5", outputPdf);

Condition 3:

SelectPages(inputPdf, "1-5", outputPdf);

Here's the comment from the iTextSharp source code on what makes up a page selection. This is in the SequenceList class which is used to process a page selection:

/**
* This class expands a string into a list of numbers. The main use is to select a
* range of pages.
* <p>
* The general systax is:<br>
* [!][o][odd][e][even]start-end
* <p>
* You can have multiple ranges separated by commas ','. The '!' modifier removes the
* range from what is already selected. The range changes are incremental, that is,
* numbers are added or deleted as the range appears. The start or the end, but not both, can be ommited.
*/