大規模PDFでのヘッダーとフッターの高速化

using IronPdf;
var pdf = PdfDocument.FromFile("input.pdf");
string headerHtml = "<div style='font-size:10px;'>Header</div>";
string footerHtml = "<div style='text-align:right;font-size:10px;'>Page {page} of {total-pages}</div>";
int chunkSize = 300;
var pageChunks = Enumerable.Range(0, pdf.PageCount)
    .GroupBy(i => i / chunkSize)
    .Select(g => g.ToArray())
    .ToList();
var tempFiles = new List<string>();
foreach (var indexes in pageChunks)
{
    var chunkPdf = pdf.CopyPages(indexes);
    int globalStartPage = indexes.First() + 1;
    chunkPdf.AddHtmlHeadersAndFooters(new ChromePdfRenderOptions
    {
        FirstPageNumber = globalStartPage,          // keeps numbering continuous
        HtmlHeader = new HtmlHeaderFooter { HtmlFragment = headerHtml, MaxHeight = 40 },
        HtmlFooter = new HtmlHeaderFooter { HtmlFragment = footerHtml, MaxHeight = 40 }
    });
    string tempFile = Path.GetTempFileName() + ".pdf";
    chunkPdf.SaveAs(tempFile);
    chunkPdf.Dispose();
    tempFiles.Add(tempFile);
}
// Merge the chunks back into one document.
var finalPdf = new PdfDocument(tempFiles.First());
foreach (var file in tempFiles.Skip(1))
{
    using var part = new PdfDocument(file);
    finalPdf.AppendPdf(part);
}
finalPdf.SaveAs("output.pdf");
finalPdf.Dispose();
// Clean up temp files.
foreach (var file in tempFiles)
    File.Delete(file);

Imports IronPdf
Imports System.IO
Imports System.Linq

Dim pdf = PdfDocument.FromFile("input.pdf")
Dim headerHtml As String = "<div style='font-size:10px;'>Header</div>"
Dim footerHtml As String = "<div style='text-align:right;font-size:10px;'>Page {page} of {total-pages}</div>"
Dim chunkSize As Integer = 300
Dim pageChunks = Enumerable.Range(0, pdf.PageCount) _
    .GroupBy(Function(i) i \ chunkSize) _
    .Select(Function(g) g.ToArray()) _
    .ToList()
Dim tempFiles = New List(Of String)()

For Each indexes In pageChunks
    Dim chunkPdf = pdf.CopyPages(indexes)
    Dim globalStartPage As Integer = indexes.First() + 1
    chunkPdf.AddHtmlHeadersAndFooters(New ChromePdfRenderOptions With {
        .FirstPageNumber = globalStartPage,
        .HtmlHeader = New HtmlHeaderFooter With {.HtmlFragment = headerHtml, .MaxHeight = 40},
        .HtmlFooter = New HtmlHeaderFooter With {.HtmlFragment = footerHtml, .MaxHeight = 40}
    })
    Dim tempFile As String = Path.GetTempFileName() & ".pdf"
    chunkPdf.SaveAs(tempFile)
    chunkPdf.Dispose()
    tempFiles.Add(tempFile)
Next

' Merge the chunks back into one document.
Dim finalPdf = New PdfDocument(tempFiles.First())
For Each file In tempFiles.Skip(1)
    Using part = New PdfDocument(file)
        finalPdf.AppendPdf(part)
    End Using
Next
finalPdf.SaveAs("output.pdf")
finalPdf.Dispose()

' Clean up temp files.
For Each file In tempFiles
    File.Delete(file)
Next