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To dynamically widen an HTML-generated PDF in iText, choose the page width before layout, set that width on the PdfDocument, and give pdfHTML the same width as its screen-media viewport. This keeps page geometry and responsive CSS aligned. iText does not transparently resize a page after HTML has already been laid out; if the width is unknown, determine it in your application or use a separate measurement strategy before conversion.
Decide what “dynamic width” means
There are four different requirements commonly described as a dynamic PDF width. Select the one that matches your output contract before writing code.
| Requirement | Recommended approach | Trade-off |
|---|---|---|
| A known or bounded width, such as a table width supplied by your application | Create a custom PageSize before conversion |
Your code must obtain the width; iText does not infer arbitrary HTML width automatically |
| Responsive CSS should react to the PDF width | Set the PDF page width and the pdfHTML screen-media width to the same value | Both settings must stay synchronized |
| One long page whose final height follows the rendered content | Start with a tall page, convert to a Document, measure the ending vertical position, then change the media box |
The documented recipe measures height, assumes one page, and does not discover horizontal width |
| A4, Letter, or another fixed output size must be preserved | Render on a page large enough for the HTML, then scale each page onto the required size | Text, images, and spacing all become smaller |
The examples below assume Java with iText 7 and pdfHTML. Method names can vary by dependency generation, so verify them against the version installed in your build.
Set a custom width before converting HTML
When your application knows the required width, create the page first. A PDF user unit is normally 1/72 inch, but you can calculate the value from your own units. The height is a separate decision: use a normal page height for pagination, or a deliberately tall page only when you are producing a single continuous page.
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PageSize pageSize = new PageSize(targetWidth, targetHeight);
PdfWriter writer = new PdfWriter(destination);
PdfDocument pdf = new PdfDocument(writer);
pdf.setDefaultPageSize(pageSize);
ConverterProperties properties = new ConverterProperties();
HtmlConverter.convertToPdf(htmlInputStream, pdf, properties);
pdf.close();targetWidth must be established before HtmlConverter lays out the document. Typical sources include a report configuration, a known column model, a user-selected paper format, or a bounded width chosen by your service. Do not claim that this code measures an arbitrary DOM and then resizes the page; it only applies the width you supply.
Keep responsive CSS and PDF geometry in sync
pdfHTML evaluates responsive rules through a media description. If your HTML uses media queries, set the screen width to the same value as the PDF page width. Otherwise CSS can choose a breakpoint for one width while the PDF page has another, producing unexpected wrapping or clipped tables.
PageSize pageSize = new PageSize(targetWidth, targetHeight);
PdfDocument pdf = new PdfDocument(new PdfWriter(destination));
pdf.setDefaultPageSize(pageSize);
ConverterProperties properties = new ConverterProperties();
MediaDeviceDescription media = new MediaDeviceDescription(MediaType.SCREEN);
media.setWidth(targetWidth);
properties.setMediaDeviceDescription(media);
HtmlConverter.convertToPdf(htmlInputStream, pdf, properties);
pdf.close();In the official responsive pattern, the width passed to the media description is derived from the selected page size (using iText’s CSS dimension parsing utilities). You can instead pass a numeric width directly when your application already works in user units. Keep the page width and media width as one configuration value rather than maintaining two independent constants.
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Known table or report width
Calculate the width from the columns, cell padding, borders, and any fixed margins before creating PageSize. Add a safety allowance for borders and rounding. If the report can grow, cap the value at a maximum your viewers support and decide whether excess content should wrap or paginate.
Responsive breakpoint width
Choose a viewport width that corresponds to the layout you want (for example, the desktop breakpoint), then use that same value for PageSize and MediaDeviceDescription. This is more predictable than allowing CSS to switch layouts midway through a report.
Width discovered from HTML
There is no general “convert, inspect every horizontal box, and transparently enlarge the page” switch. A reliable implementation needs a measurement pass or application-level knowledge of the widest element, followed by a fresh conversion using the measured width. Validate the result with the actual fonts, images, CSS, and margins used in production; layout can change when those inputs change.
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One-page documents: measure height separately
iText’s documented one-page report technique solves a different problem: fitting the final height to rendered content. It starts with a page width (the example uses 595 user units) and a very tall page (14,400 units), converts with convertToDocument, records the final Y position through a custom line separator, and then changes the first page’s media box to the required height.
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Viewer limits also matter. iText documents 14,400 user units as an Adobe Acrobat/Reader implementation limit for rendering page width or height. A page larger than that may appear blank in those viewers, even if the PDF file was created successfully. Keep both dimensions below the limit when Acrobat/Reader compatibility is required, or paginate instead of creating an extreme single page.
Keep a standard page by scaling oversized HTML
If a print contract requires A4, Letter, or another fixed size, increasing the page width is the wrong output model. The documented alternative is to render the HTML on a page large enough to contain it, copy each rendered page to a PdfFormXObject, and place that object on the target page with a scale factor.
Scaling preserves the prescribed media box, but it changes the physical size of everything: text, lines, images, and whitespace. Test readability, accessibility, and multi-page placement before adopting it. If the result is too small, wrapping or pagination is usually preferable to more aggressive scaling.
Using CSS @page
pdfHTML support information lists @page and its size property, including custom dimensions such as 210mm 297mm, as supported. You can therefore express a paper choice in HTML/CSS:
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@page {
size: 320mm 210mm;
margin: 12mm;
}
Treat this as pdfHTML-specific behavior, not full browser print-engine equivalence. The same support information lists overflow handling and named-page selection through the page property as unsupported. Confirm behavior against the pdfHTML version deployed by your application, especially after upgrades. For a width supplied dynamically by Java, setting the PdfDocument default page size remains the clearest control.
Complete implementation pattern
The following method separates width selection from conversion and keeps the CSS viewport synchronized. It uses a normal page height so content can paginate.
public static void htmlToPdf(
InputStream html,
OutputStream destination,
float targetWidth,
float targetHeight) throws IOException {
PageSize pageSize = new PageSize(targetWidth, targetHeight);
PdfDocument pdf = new PdfDocument(new PdfWriter(destination));
pdf.setDefaultPageSize(pageSize);
ConverterProperties properties = new ConverterProperties();
MediaDeviceDescription screen =
new MediaDeviceDescription(MediaType.SCREEN);
screen.setWidth(targetWidth);
properties.setMediaDeviceDescription(screen);
HtmlConverter.convertToPdf(html, pdf, properties);
pdf.close();
}For a real service, close the PDF in a finally or try-with-resources design appropriate to your iText version, validate positive dimensions, and reject widths above your viewer or operational limit. If conversion throws, do not return the partially written file as a successful document.
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Troubleshooting dynamic-width PDFs
Columns are cut off
- Check that the supplied
PageSizewidth includes margins, borders, and cell padding. - Verify that the media-device width equals the page width when responsive CSS is involved.
- Look for fixed-width CSS or unbreakable strings that exceed the chosen width.
The layout uses the mobile breakpoint
The CSS viewport is probably narrower than the PDF page, or no screen media description was configured. Set MediaType.SCREEN and the intended width before conversion.
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Changing the media box did not reflow text
Changing a page’s box after conversion changes geometry, not the already-computed line breaks. Convert again with the new width.
The one-page PDF is blank in Acrobat
Check whether width or height exceeds 14,400 user units. Reduce the page, paginate, or render and scale onto a standard page.
CSS @page appears ignored
Confirm the deployed pdfHTML version and its CSS support. Avoid relying on unsupported overflow or named-page features, and set the page size in Java when the value is generated by application data.
Output is tiny after fitting Letter or A4
That is the expected consequence of scaling a large rendering onto a fixed page. Reduce the source width, allow wrapping and pagination, or accept a larger physical output page.
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- Choose whether width is known, measured, responsive, or constrained by a fixed paper size.
- Set
PdfDocumentpage geometry before callingHtmlConverter. - Match screen-media width to page width when media queries matter.
- Decide explicitly between pagination and one long page.
- Keep one-page dimensions under the 14,400-user-unit viewer limit when Acrobat/Reader support is required.
- Test fonts, images, long words, tables, margins, and the widest real dataset.
- Reconvert after any width change; do not expect post-layout resizing to reflow content.
Frequently Asked Questions
Can iText automatically grow a PDF page to the widest HTML element?
Not as a transparent post-layout operation. Determine the width before conversion, or run an appropriate measurement process and convert again with the resulting width.
Should I use a wider page or scale onto A4?
Use a wider page when preserving physical text size is important. Scale only when the output must remain a fixed paper size and the resulting smaller content is acceptable.
Does a custom width require a special browser?
No. pdfHTML performs the conversion in Java; the important controls are the PDF page size and, for responsive layouts, the screen-media width.
The Bottom Line
Set the target width before pdfHTML lays out the document, use the same value for responsive screen media, and choose pagination or scaling deliberately when the width cannot remain arbitrary.
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