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How to Render PDFs with Custom Paper Size

Chaknith Bin

Updated:July 28, 2025

A custom paper size refers to a non-standard paper size that is defined by the user rather than being a standard size like A4 or letter size (8.5 x 11 inches). Custom paper sizes are often used when printing documents that require a unique or specific layout, such as posters, banners, or specialty documents.

Discover the extensive range of paper sizes available with IronPDF, offering a wide selection to suit your needs!

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First Step:

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Use Standard Paper Size Example

First, create an instance of the ChromePdfRenderer class. Then, use the RenderingOptions property of the newly created object to modify the PaperSize. Set it to one of the predefined values from the PdfPaperSize enum to specify the desired paper size. We offer over 100 predefined standard paper sizes for your convenience.

Code

Below is an example of how to set a standard paper size:

:path=/static-assets/pdf/content-code-examples/how-to/custom-paper-size-standard-paper-size.cs

using IronPdf;
using IronPdf.Rendering;

ChromePdfRenderer renderer = new ChromePdfRenderer();

// Set paper size to A4
renderer.RenderingOptions.PaperSize = PdfPaperSize.A4;

PdfDocument pdf = renderer.RenderHtmlAsPdf("<h1>Standard Paper Size</h1>");

pdf.SaveAs("standardPaperSize.pdf");

Imports IronPdf
Imports IronPdf.Rendering

Private renderer As New ChromePdfRenderer()

' Set paper size to A4
renderer.RenderingOptions.PaperSize = PdfPaperSize.A4

Dim pdf As PdfDocument = renderer.RenderHtmlAsPdf("<h1>Standard Paper Size</h1>")

pdf.SaveAs("standardPaperSize.pdf")

Related Properties

• PaperSize: Set an output paper size for PDF pages with predefined sizes such as letter, A3, A4, etc.
• ForcePaperSize: Forces page sizes to be exactly what is specified via IronPdf.ChromePdfRenderOptions.PaperSize by resizing the page after generating a PDF from HTML. This feature is useful for bypassing CSS rules that specify paper size.

Get Standard Paper Sizes in Various Units

Need to find the dimensions of standard paper sizes? You can easily do so using the ToMillimeters method. This method returns a tuple containing the width and height of the standard paper size as Length objects. The Length class is incredibly versatile, allowing you to effortlessly convert these dimensions into a variety of units, including:

• Millimeters
• Centimeters
• Inches
• Pixels
• Points

:path=/static-assets/pdf/content-code-examples/how-to/custom-paper-size-standard-paper-size-in-other-unit.cs

using IronPdf.Rendering;

double A4WidthInPixel = PdfPaperSize.A4.ToMillimeters().width.ToPixel();
double A4HeightInCentimeter = PdfPaperSize.A4.ToMillimeters().height.ToCentimeter();

Imports IronPdf.Rendering

Private A4WidthInPixel As Double = PdfPaperSize.A4.ToMillimeters().width.ToPixel()
Private A4HeightInCentimeter As Double = PdfPaperSize.A4.ToMillimeters().height.ToCentimeter()

Use Custom Paper Size Example

First, we begin by instantiating the ChromePdfRenderer class. From the newly created object, we can access the RenderingOptions to apply a custom paper size to the newly generated PDF document. There are four methods that can be used to set the output paper size for PDF pages, each based on a different measurement unit:

• SetCustomPaperSizeInCentimeters: Dimensions are in centimeters.
• SetCustomPaperSizeInInches: Dimensions are in inches.
• SetCustomPaperSizeInMillimeters: Dimensions are in millimeters.
• SetCustomPaperSizeInPixelsOrPoints: Dimensions are in pixels or points.

Code

Below is an example of how to set a custom paper size in centimeters:

:path=/static-assets/pdf/content-code-examples/how-to/custom-paper-size-cm.cs

using IronPdf;

ChromePdfRenderer renderer = new ChromePdfRenderer();

// Set custom paper size in cm
renderer.RenderingOptions.SetCustomPaperSizeinCentimeters(15, 15);

PdfDocument pdf = renderer.RenderHtmlAsPdf("<h1>Custom Paper Size</h1>");

pdf.SaveAs("customPaperSize.pdf");

Imports IronPdf

Private renderer As New ChromePdfRenderer()

' Set custom paper size in cm
renderer.RenderingOptions.SetCustomPaperSizeinCentimeters(15, 15)

Dim pdf As PdfDocument = renderer.RenderHtmlAsPdf("<h1>Custom Paper Size</h1>")

pdf.SaveAs("customPaperSize.pdf")

Output PDF

Modify Paper Dimension Example

In an existing PDF document or a freshly rendered PDF, the size of each page can be modified using the ExtendPage method. This method allows you to specify the target page index, the values to modify each of the four sides, and the units of measurement. The values for each side can be negative, which will reduce that particular side, or positive, which will extend that side.

Code

Below is an example of how to modify paper dimensions:

:path=/static-assets/pdf/content-code-examples/how-to/custom-paper-size-modify-paper-size.cs

using IronPdf;
using IronPdf.Editing;

PdfDocument pdf = PdfDocument.FromFile("customPaperSize.pdf");

pdf.ExtendPage(0, 50, 0, 0, 0, MeasurementUnit.Millimeter);

pdf.SaveAs( "extendedLeftSide.pdf");

Imports IronPdf
Imports IronPdf.Editing

Private pdf As PdfDocument = PdfDocument.FromFile("customPaperSize.pdf")

pdf.ExtendPage(0, 50, 0, 0, 0, MeasurementUnit.Millimeter)

pdf.SaveAs("extendedLeftSide.pdf")

Output PDF

Ready to see what else you can do? Check out our tutorial page here: Create PDFs

Chaknith Bin

  Chat with engineering team now

Software Engineer

Chaknith works on IronXL and IronBarcode. He has deep expertise in C# and .NET, helping improve the software and support customers. His insights from user interactions contribute to better products, documentation, and overall experience.

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