---
title: "Page geometry: boxes, rotation and user unit"
url: https://recursiveai.org/onepdf/docs/page-geometry/
description: "Every page has a media box and optional crop, bleed, trim and art boxes, a clockwise /Rotate and a /UserUnit (ISO 32000-2 7.7.3.3, Table 31; 14.11.2).…"
version: "1.20.0"
source: https://github.com/recursive-ai-oss/onepdf-csharp/blob/b66f5336c353be4d6f6d337a198719983d92a72e/docs/page-geometry.md
---

# Page geometry: boxes, rotation and user unit

Every page has a media box and optional crop, bleed, trim and art boxes, a clockwise `/Rotate` and a `/UserUnit` (ISO 32000-2 7.7.3.3, Table 31; 14.11.2). OnePDF reads and writes all of them.

## Reading

- `page.MediaBox`, `CropBox`, `BleedBox`, `TrimBox`, `ArtBox` are the *effective* rectangles. The media box and crop box and `Rotate` are inherited from the page tree. The crop box defaults to the media box; the other three default to the crop box. Every box is clipped to the media box (a box that misses it reads as its default). A malformed entry reads as its default with a diagnostic.
- `page.GetBox(PdfPageBox)` is the same by name, and `page.HasExplicitBox(PdfPageBox)` tells a stored box from a default.
- `page.GetDisplaySize(box, applyRotate, applyUserUnit)` returns a `PdfPageSize`: points after `/Rotate` (width and height swap at 90 and 270) and `/UserUnit`, with `WidthInches`, `HeightInches`, `WidthMillimeters` and `HeightMillimeters`. The interpreter's `PdfInterpretOptions.Box` uses the same box choice.
- `page.GetBoxColorInfo(box)` returns the page's `/BoxColorInfo` entry for the crop, bleed, trim or art box (colour, line width, solid or dashed with dash pattern; Table 394 defaults), or null.

## Editing existing pages (`AllowEditing`)

```csharp
using var doc = PdfDocument.Open(path, new PdfOpenOptions { AllowEditing = true });
PdfPage page = doc.Pages[0];
page.SetTrimBox(new PdfRectangle(36, 36, 264, 264));
page.ClearBleedBox();
page.SetRotate(90);
page.SetUserUnit(2);
page.SetBoxColorInfo(PdfPageBox.TrimBox, new PdfBoxColorInfo { Blue = 1 });

doc.SetPrintGeometry(bleed: 9);                        // every page: keep trim, media = bleed = trim + 9 pt
page.SetPrintGeometry(new PdfRectangle(36, 36, 264, 264), 9); // one page, explicit trim
doc.Save(output);                                      // or SaveIncremental
```

- Every setter writes on the page itself. An inherited media box, crop box or rotation is overridden; the page-tree node is not changed.
- Rectangles are normalized when written (any two opposite corners are accepted). Non-finite or empty rectangles, a `Rotate` that is not a multiple of 90 (negative values and values over 360 are normalized), and a `UserUnit` that is not finite and positive throw `ArgumentException`; nothing is changed.
- `Clear*` returns a box to its default. For the crop box and `Rotate`, which can be inherited, an inherited value is overridden on the page with the default (the media box, 0).
- **Shrinking the media box** clips the page's own crop, bleed, trim and art boxes to it and removes one that no longer overlaps it, so what is stored matches what a reader reports.
- **`SetPrintGeometry`** sets the trim box; the media and bleed boxes become the trim box grown by the bleed; the crop box is cleared. Content keeps its coordinates.
- `SetUserUnit` raises the document version to 1.6, where `/UserUnit` was introduced.
- The page objects update in place: a page you hold reports the new values straight away, and `Save`/`SaveIncremental` write them. Reopening the saved file gives the same values.
- `PdfDocument.RotatePage` adds to the rotation; `PdfDocument.SetPageRotation` sets it by index. `page.SetRotate` is the same on a page object.

## Creating pages

`PdfDocumentWriter.BeginPage(width, height, rotate)` starts a page whose media box is `[0 0 width height]`. Before `Commit`, the builder takes `SetCropBox`, `SetBleedBox`, `SetTrimBox`, `SetArtBox` and `SetUserUnit`. `BeginPrintPage(trimWidth, trimHeight, bleed, rotate)` is the one-liner: media and bleed box are the trim size plus the bleed on every side, the trim box sits at `(bleed, bleed)`, and drawing coordinates start at the lower left of the media box. `PdfDocument.InsertBlankPage` returns a `PdfPage`, so the editing calls above work on it.

## PDF/A

ISO 19005-2 6.1.13 limits every page box to 3 to 14400 units on each side; the PDF/A checker applies it to the boxes written here.