What is the difference between "cropping" and "resizing" a PDF?

Cropping changes which part of each page is visible without changing the page contents. The PDF still contains the original full page, but the visible "page box" is smaller — only the in-bounds region is shown by viewers and printed by printers. Resizing actually changes the page dimensions, scaling the contents up or down to fit. Both feel similar when you look at the result, but they behave differently: cropped PDFs preserve the original content (you can un-crop later by adjusting the page box back); resized PDFs permanently change the scale (text gets bigger or smaller depending on direction). For removing whitespace, crop. For changing target paper size, resize.

How do I know which page box I am editing — MediaBox, CropBox, BleedBox, TrimBox, ArtBox?

PDF defines five page boxes per the ISO 32000-1 specification. MediaBox is the physical paper size; everything else is a subset. CropBox is what most viewers display by default; "cropping" a PDF really means setting the CropBox smaller than the MediaBox. TrimBox is the intended final size after cutting (used in print production); BleedBox is the area where bleed elements extend; ArtBox is the meaningful content rectangle. For non-print use cases, only MediaBox and CropBox matter — the other three exist for press workflows. Most tools labeled "Crop PDF" set the CropBox; tools labeled "Resize PDF" change the MediaBox.

I cropped the PDF but the content still shows when I open it in another viewer. Why?

Some viewers ignore the CropBox and display the full MediaBox — including the parts you cropped out. Apple Preview is a common culprit; Acrobat Reader and modern Chrome respect CropBox correctly. The fix depends on intent. If the cropped content must never display anywhere, use "destructive crop": remove the content outside the crop region entirely so the MediaBox itself shrinks. ScoutMyTool Crop PDF offers a "Trim destructively" option that does this. If you only need the crop for display in standard viewers, the CropBox-only approach is enough.

My PDF prints with small text and large margins. How do I make it print full size?

Three likely causes. First, the print dialog has "Fit to printable area" enabled — uncheck it and select "Actual size" instead. Second, the PDF page size is smaller than the paper (e.g. A5 content on Letter paper); resize the PDF to match the paper, then print. Third, the printer has a hardware unprintable margin (usually 0.25–0.5" all around) and the PDF cannot print to the edge regardless; the only fix is a printer with edge-to-edge capability or to shrink the design to fit within the printable area. For posters and brochures intended to print edge-to-edge, plan for a 0.5" border in the design or commission a commercial print shop.

How do I add margins to a PDF that has none?

Use the "resize page, keep content centred" workflow. In ScoutMyTool Resize PDF, choose "Expand page", set the new page size (e.g. add 1 inch to each dimension), and select "centre content". The result has the same content as before but with new whitespace margins around the edges. This is useful when you need to add space for annotations, page numbers, or binding allowance. Note that this changes the MediaBox, so the page is now bigger overall — print at "Actual size" to preserve the new margins.

Can I crop different pages of a PDF differently?

Yes. In ScoutMyTool Crop PDF, after setting the crop rectangle, choose "Apply to: this page only" or "all pages" or "page range". Most cropping tools support per-page or per-range cropping — Acrobat Pro and PDFsam both do. Use per-page cropping when your PDF mixes content of different sizes (a research paper with appendix scans, or a mixed-orientation document). The output PDF can have varying page sizes, which is fully valid PDF (the MediaBox is per-page, not per-file).

After cropping, my PDF file size is the same. Is the cropped content really removed?

Not necessarily. Standard cropping changes the CropBox metadata only — the original page contents remain in the file, just clipped from view. File size stays similar (or even increases slightly because of the added metadata). To actually shrink the file, run a "trim destructively" or "flatten and re-export" step that rewrites the content stream to exclude the cropped-out region. ScoutMyTool Crop PDF's "Trim destructively" option does this in one click. After destructive trimming, compress the file to remove any residual structural overhead.

How to fix PDF margins — cropping, resizing, page setup (2026)

7 min read

How to fix PDF margins — cropping, resizing, page setup

By ScoutMyTool Editorial Team · Last updated: 2026-05-20

A two-inch grey border on every scanned chapter, an architectural drawing trimmed at the right edge, an annual report whose pages alternate between Letter and A4 — all three landed in my inbox last quarter and all three needed a different fix. PDF margins go wrong for a few well-defined reasons, and once you can match the symptom to the cause the fix takes about 30 seconds. This article maps the six common PDF margin problems, the underlying cause of each, and the free tool that handles them without subscribing to anything or uploading the file.

Diagnose the symptom, pick the fix

Symptom	Cause	Fix
Huge white margins on a scanned PDF	Scanner captured the whole platen including blank area around the document	Crop using the trim-to-content feature — auto-detects content bounds and removes whitespace
Text or images cut off at the edges	Source export used a smaller paper size than the content (Letter content exported to A5)	Resize page to fit content, or re-export from source with correct paper size
Pages alternate between two different sizes	PDF was assembled from multiple sources (mix of Letter and A4, mix of portrait and landscape)	Normalise all pages to a single size with the resize feature; pick the largest dimension to preserve content
Printed PDF has small margins on top, large on bottom (or vice versa)	Print driver applied "fit to page" with non-uniform scaling, or the PDF page box mismatches print box	Set PDF page box to match the target paper size (Letter, A4, etc.) using the page-setup tool
Different left/right margins on odd vs even pages	PDF was set up for two-sided printing (binding offset) but is being viewed single-sided	This is correct for two-sided print and bound documents; do not "fix" unless the document is now single-sided
Page numbers or headers fall in the trim margin when printed	Page numbers placed inside the typical 0.5" printer-unprintable area; printer cannot print to the edge	Move page numbers in by 0.5" from each edge, or print on a printer with edge-to-edge capability

Step by step — auto-trim whitespace from a scanned PDF

Open ScoutMyTool Crop PDF at scoutmytool.com/pdf/crop-pdf and drag the source PDF into the drop zone. The tool runs in your browser; the file does not upload. Page thumbnails appear with their current page boxes outlined in blue.
Choose "Auto-detect content bounds". The tool scans each page, identifies the bounding rectangle around the non-white content, and proposes a crop. Page thumbnails update to show the proposed crop in green over the existing blue page box. If a thumbnail looks wrong (e.g. detected too tight, cutting into actual content), you can adjust individually in the next step.
Tune any outliers manually. Click a problem page thumbnail to enter manual mode. Drag the green crop handles to extend or shrink the crop. For consistency across pages (e.g. all chapters should match), use "Apply this crop to all pages" — useful when the auto-detect over-tightened a few pages.
Pick CropBox-only or destructive trim. CropBox-only mode is non-destructive: the cropped-out content remains in the file but is hidden from viewers. Destructive trim removes the cropped-out content entirely, reducing file size and ensuring the trimmed area never reappears in any viewer.
Export and verify. Download the cropped PDF. Open in two different viewers (Acrobat Reader and Apple Preview, or Chrome and Firefox). The cropped page should look identical in both — if not, switch to destructive trim mode and re-export. Spot-check the first, middle, and last page for content integrity.

Tool comparison

Tool	Cost	Crop modes	Privacy
ScoutMyTool Crop PDF	Free	Auto-detect + manual handles	Client-side — no upload
ScoutMyTool Resize PDF	Free	Fit content, fit paper, custom	Client-side — no upload
Adobe Acrobat Pro — Crop	$19.99/mo	Manual + auto-detect	Local desktop / cloud sync
Apple Preview — Tools → Crop	Free, macOS	Manual rectangle drag	Local
PDFsam (open source)	Free	Manual via crop module	Local

Crop a PDF: deeper coverage of cropping mechanics.
Compress PDF: pair with destructive trim to actually shrink file size.
Add page numbers to a PDF: place numbers inside the printable area.
Remove pages from a PDF: when "fixing margins" really means "remove the blank page".
Edit a scanned PDF: cropping is part of the cleanup; OCR and de-skew are the rest.
Make a transparent PDF: when "remove white margin" means "remove white background".
ScoutMyTool Crop PDF: the tool — free, browser-based.

FAQ

What is the difference between "cropping" and "resizing" a PDF?: Cropping changes which part of each page is visible without changing the page contents. The PDF still contains the original full page, but the visible "page box" is smaller — only the in-bounds region is shown by viewers and printed by printers. Resizing actually changes the page dimensions, scaling the contents up or down to fit. Both feel similar when you look at the result, but they behave differently: cropped PDFs preserve the original content (you can un-crop later by adjusting the page box back); resized PDFs permanently change the scale (text gets bigger or smaller depending on direction). For removing whitespace, crop. For changing target paper size, resize.
How do I know which page box I am editing — MediaBox, CropBox, BleedBox, TrimBox, ArtBox?: PDF defines five page boxes per the ISO 32000-1 specification. MediaBox is the physical paper size; everything else is a subset. CropBox is what most viewers display by default; "cropping" a PDF really means setting the CropBox smaller than the MediaBox. TrimBox is the intended final size after cutting (used in print production); BleedBox is the area where bleed elements extend; ArtBox is the meaningful content rectangle. For non-print use cases, only MediaBox and CropBox matter — the other three exist for press workflows. Most tools labeled "Crop PDF" set the CropBox; tools labeled "Resize PDF" change the MediaBox.
I cropped the PDF but the content still shows when I open it in another viewer. Why?: Some viewers ignore the CropBox and display the full MediaBox — including the parts you cropped out. Apple Preview is a common culprit; Acrobat Reader and modern Chrome respect CropBox correctly. The fix depends on intent. If the cropped content must never display anywhere, use "destructive crop": remove the content outside the crop region entirely so the MediaBox itself shrinks. ScoutMyTool Crop PDF offers a "Trim destructively" option that does this. If you only need the crop for display in standard viewers, the CropBox-only approach is enough.
My PDF prints with small text and large margins. How do I make it print full size?: Three likely causes. First, the print dialog has "Fit to printable area" enabled — uncheck it and select "Actual size" instead. Second, the PDF page size is smaller than the paper (e.g. A5 content on Letter paper); resize the PDF to match the paper, then print. Third, the printer has a hardware unprintable margin (usually 0.25–0.5" all around) and the PDF cannot print to the edge regardless; the only fix is a printer with edge-to-edge capability or to shrink the design to fit within the printable area. For posters and brochures intended to print edge-to-edge, plan for a 0.5" border in the design or commission a commercial print shop.
How do I add margins to a PDF that has none?: Use the "resize page, keep content centred" workflow. In ScoutMyTool Resize PDF, choose "Expand page", set the new page size (e.g. add 1 inch to each dimension), and select "centre content". The result has the same content as before but with new whitespace margins around the edges. This is useful when you need to add space for annotations, page numbers, or binding allowance. Note that this changes the MediaBox, so the page is now bigger overall — print at "Actual size" to preserve the new margins.
Can I crop different pages of a PDF differently?: Yes. In ScoutMyTool Crop PDF, after setting the crop rectangle, choose "Apply to: this page only" or "all pages" or "page range". Most cropping tools support per-page or per-range cropping — Acrobat Pro and PDFsam both do. Use per-page cropping when your PDF mixes content of different sizes (a research paper with appendix scans, or a mixed-orientation document). The output PDF can have varying page sizes, which is fully valid PDF (the MediaBox is per-page, not per-file).
After cropping, my PDF file size is the same. Is the cropped content really removed?: Not necessarily. Standard cropping changes the CropBox metadata only — the original page contents remain in the file, just clipped from view. File size stays similar (or even increases slightly because of the added metadata). To actually shrink the file, run a "trim destructively" or "flatten and re-export" step that rewrites the content stream to exclude the cropped-out region. ScoutMyTool Crop PDF's "Trim destructively" option does this in one click. After destructive trimming, compress the file to remove any residual structural overhead.

Citations

ISO 32000-1:2008 — "Document management — Portable document format" — §14.11 (Page Boundaries) defining MediaBox, CropBox, BleedBox, TrimBox, ArtBox.
Adobe — "Set page boxes" — Acrobat Pro documentation of the five PDF page boxes.
ISO 216 — paper size standard (A4, A5, etc.) — the international paper-size reference.
ANSI/ASME Y14.1 — US paper size standard (Letter, Legal, etc.) — the US paper-size reference.

Fix margins in your browser

ScoutMyTool Crop PDF and Resize PDF both run client-side — no upload, no account. Trim whitespace, normalise page sizes, or add binding margins in seconds.

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