Resize PDF FREE | Change PDF Page Size Online

Change the page size of any PDF to A4, A3, A5, Letter, Legal, Tabloid, or any custom dimension. The content of every page is automatically scaled to fit and centred on the new page. All pages are processed and downloaded as a single PDF. Free, private, runs entirely in your browser.

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PDF Page Resizer

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Frequently Asked Questions

Each page of your PDF is rendered at high resolution using PDF.js, which is Mozilla's open-source PDF rendering engine. The rendered page image is then embedded into a new blank page at your chosen target size using pdf-lib. The scaling algorithm calculates the largest size the content can be without exceeding the target dimensions minus your margin, then positions it exactly in the centre of the new page both horizontally and vertically. The output is a standard PDF file with all pages at the new size.

No. The scaling maintains the exact original aspect ratio of each page. The content is scaled proportionally to fit within the target dimensions, never stretched or squashed. If the original page and the target size have different aspect ratios, the content fills either the full width or full height of the available area and is centred in the remaining space. White space appears on the sides or top and bottom as needed.

The margin setting adds empty space between the edge of the new page and the scaled content. A 10mm margin means the content is scaled to fit within a box that is 10mm smaller on each side than the full page. This prevents content from touching the page edge, which is important if the output will be printed and trimmed. Set the margin to 0 for maximum content size with no border.

The preset sizes are A3, A4, A5, B4, B5, Letter (US), Legal (US), and Tabloid (US). Custom mode lets you type any width and height in millimetres, inches, or pixels. Both portrait and landscape orientations are available for all presets. Common conversions include resizing a US Letter PDF to A4 for European printing, or resizing a presentation PDF from custom dimensions to A4 for filing and archiving.

Yes. Every page in the PDF is processed and resized to the same target dimensions. All pages are assembled into a single output PDF in the original order. Progress is shown as each page is processed. The output file downloads automatically when all pages are complete.

No. The PDF is processed entirely in your browser. PDF.js renders the pages locally and pdf-lib builds the output PDF locally. Nothing is sent to any server at any point. This is especially important for confidential documents such as contracts, financial statements, or personal paperwork.

When content is scaled to fit inside a larger page, empty space appears around the content. The page background colour fills that space. White is the standard for documents. Black can be used for presentation PDFs where a dark border looks intentional. Any colour can be selected using the colour picker.

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Free PDF Page Resizer Online - Change Any PDF to A4, Letter, A3 or Custom Size Instantly

The page size of a PDF is one of those technical details that becomes a significant problem the moment it does not match requirements. A contract created in the United States on Letter paper needs to be filed in a European system that only accepts A4. A presentation slide PDF created at custom 1920x1080 pixel dimensions needs to be printed on standard A4 paper. A scanned document at an unusual size needs to be standardised before submission to a government portal. A brochure PDF at A4 needs to be reprinted on A3 without redesigning the layout. These are extremely common real-world scenarios and the PDF Page Resizer on OneDocPDF solves all of them in seconds, running entirely in your browser with no upload required.

The tool renders each PDF page at high resolution using PDF.js and embeds it as an image into a new page at your target dimensions, scaled proportionally and centred. This approach works on every type of PDF content including scanned documents, digital text documents, vector graphics, mixed-content pages, and presentation slides. The output maintains visual fidelity because the render resolution is set high enough that text and graphics remain sharp even after scaling. The margin control adds breathing room around the content so it never touches the page edge, which is essential for documents that will be physically printed and trimmed.

Converting between Letter and A4 is the single most common PDF resize operation globally. Letter (216 x 279mm) is slightly wider and shorter than A4 (210 x 297mm). When a Letter PDF is printed on an A4 printer without adjustment, the content is either clipped or scaled with uneven margins. When an A4 PDF is printed on Letter paper in the United States without adjustment, content near the bottom is cut off. This resizer scales the content to fit perfectly within the new page margins and centres it, eliminating the problem permanently. The same logic applies in reverse for A4 to Letter conversion.

The A3 to A4 and A4 to A3 conversions are common in architectural, engineering, and design workflows. Technical drawings are often created at A3 or larger for detail, but clients, regulatory bodies, and archives often require A4 copies for filing. Resizing an A3 engineering drawing to A4 with this tool scales the content to approximately 70.7% of its original size and centres it on the new page. Custom dimensions make this tool useful for specialised workflows beyond standard paper sizes including ebook formats, social media canvas sizes, and large-format printing preparation.

Before resizing, you may want to prepare your PDF using our other tools. Use our PDF Crop tool to trim whitespace from the original before resizing, giving you more content area in the output. Use our PDF Rotate tool to correct page orientation before changing the size. Use our Delete Pages tool to remove unwanted pages before processing a long document. Use our PDF Splitter to break a large document into sections and resize each separately if needed for different output requirements.

After resizing, you may need additional processing before the document is ready for its final destination. Use our PDF Compressor to reduce file size of the resized output before emailing or uploading. Use our Add Header and Footer to PDF tool to add page numbers, dates, or document titles to the resized pages. Use our PDF Watermark tool to add a confidential or draft stamp across all the resized pages. Use our PDF Merge tool to combine the resized PDF with other documents into a single submission package.

For workflows involving PDF to image conversion, our PDF to JPG converter extracts each page as a high-resolution image. If you need to build a new PDF from a set of images at a specific page size, use our JPG to PDF converter. For adding a signature to the resized document, our PDF Signature tool places a drawn, typed, or uploaded signature anywhere on any page. To fill in form fields on the resized document, our PDF Form Filler adds text boxes at any position.

Page orientation is a separate control from the size preset. An A4 landscape page (297 x 210mm) is a completely different format from A4 portrait (210 x 297mm). Presentations are typically landscape while documents are typically portrait. If you need to convert a portrait document to landscape to combine with landscape pages using our PDF Merge tool, simply select your target size and choose the landscape orientation. The content will be scaled and centred on the landscape page automatically.

The background colour setting is particularly important for creative and presentation PDFs. When a 16:9 widescreen slide deck PDF is resized to A4 portrait, the content takes up roughly the central 56% of the page height, leaving significant white space above and below each slide. For a professional printed handout, white background looks clean. For an internal review document, a light grey background (e.g. #f1f5f9) helps distinguish the slide area from the page background visually. For a creative portfolio or art book print layout, a black background (#000000) creates a dramatic presentation where the slide sits as a bright inset against a dark page.

Printing professionals and document controllers often need to standardise PDF page sizes across a mixed document set before combining them into a single file. A tender submission package might include a cover letter on A4, technical drawings on A3, and supporting certificates scanned at various non-standard sizes. Resizing each document to A4 before merging ensures consistent pagination, uniform headers and footers, and reliable printing across the full package. Use this resizer on each document separately, then combine the results using our PDF Merge tool to produce a single standardised submission file.

Browse the complete collection of free document tools on OneDocPDF: our PDF tools collection covers every common PDF task from conversion and compression to annotation, redaction, and page management. Our image tools collection handles photo editing, background removal, watermarking, and format conversion. Our utility tools include calculators, converters, and text processing tools. Every tool is completely free, requires no account, and processes everything locally in your browser. Visit our FAQ page for more answers or contact us through the Support Centre.