MediaSizer

User Guide — Mapsoft MediaSizer Plugin for Adobe Acrobat

Overview

MediaSizer is an Adobe Acrobat plug-in that changes the page box sizes of PDF pages. Every PDF page can have up to five different page boundary boxes — media box, crop box, trim box, bleed box, and art box — each serving a different purpose in print production and document display. MediaSizer lets you set any or all of these boxes to a standard paper size or a custom size with precise dimensions.

This is essential for print production workflows where page boxes must be set correctly for imposition, trimming, and bleed. It is also useful for normalising page sizes across a document, converting between paper standards (e.g., Letter to A4), or adding bleed areas to pages that lack them.

MediaSizer supports both portrait and landscape orientations, provides a comprehensive list of standard paper sizes, and allows you to define and save custom sizes. A scaling option controls how existing content is handled when the page size changes. All settings can be saved as named configurations for repeated use.

Getting Started

After installation, MediaSizer adds a menu item under Extensions › Mapsoft › MediaSizer in Adobe Acrobat. Click this to open the MediaSizer dialog.

Open a PDF document in Adobe Acrobat.
Go to Extensions › Mapsoft › MediaSizer.
Select which page box(es) to modify (media, crop, trim, bleed, art).
Choose a standard paper size from the dropdown, or enter custom dimensions.
Select portrait or landscape orientation.
Choose which pages to apply the change to.
Click OK to apply.

Tip: If you only need to change the media box to a standard size, select the size from the dropdown and click OK. MediaSizer handles the coordinate calculations automatically based on the current page dimensions and the selected scaling option.

Page Boxes

The PDF specification defines five page boundary boxes, each with a specific role. MediaSizer can set any combination of these boxes independently:

Page Box	Purpose	Required?
Media Box	Defines the full physical page size. This is the largest box and represents the boundaries of the physical medium (paper). All other boxes must fall within the media box.	Yes (always present)
Crop Box	Defines the visible area when the page is displayed or printed. Content outside the crop box is clipped. Defaults to the media box if not explicitly set.	No (defaults to media box)
Trim Box	Defines the intended final page size after trimming. Used in print production to indicate where the paper will be cut. Defaults to the crop box if not set.	No (defaults to crop box)
Bleed Box	Defines the area to which page content should extend to allow for trimming tolerances. Typically 3–5mm larger than the trim box on each side. Defaults to the crop box if not set.	No (defaults to crop box)
Art Box	Defines the extent of the meaningful content on the page, as intended by the creator. Used by some workflows to identify the content area. Defaults to the crop box if not set.	No (defaults to crop box)

Understanding these boxes is important for print production. For general document viewing, the media box and crop box are the most relevant. For prepress workflows, the trim box and bleed box are essential for correct imposition and finishing.

Selecting a Size

The Size dropdown provides a comprehensive list of standard paper sizes covering international (ISO), North American, and other regional standards. Common sizes include:

ISO A series — A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10
ISO B series — B0, B1, B2, B3, B4, B5, B6
ISO C series — C0, C1, C2, C3, C4, C5, C6 (envelope sizes)
North American — Letter, Legal, Tabloid/Ledger, Executive, Statement
ANSI — ANSI A through ANSI E
Architectural — Arch A through Arch E

After selecting a size, choose Portrait or Landscape orientation using the radio buttons. The dimensions displayed in the dialog update to reflect the selected size and orientation in the current measurement unit.

Scaling

The Scaling dropdown controls how existing page content is handled when the page box size changes. Options typically include centring the content on the new page size, scaling the content to fit the new dimensions, or simply repositioning the page box without modifying the content. Choose the option that best fits your workflow requirements.

Measurement Units

The Units dropdown lets you view and enter dimensions in your preferred unit: points, millimetres, centimetres, or inches. Changing the unit updates all displayed dimensions automatically.

Custom Sizes

If the standard paper sizes do not meet your needs, click the Add button to define a custom size. Enter a name for the size along with the width and height in your preferred measurement unit. Custom sizes are added to the size dropdown and are available for future use.

Custom sizes are particularly useful for non-standard output formats such as business cards, postcards, banners, or any application-specific page dimensions. Once defined, custom sizes appear alongside the standard sizes in the dropdown and are stored permanently in the plug-in's configuration file.

Tip: When working with print production, define a custom size that includes your desired bleed area. For example, if your final trim size is 210 x 297mm (A4) with 3mm bleed on each side, create a custom bleed size of 216 x 303mm.

Page Selection

MediaSizer lets you choose which pages receive the new page box size:

Current Page — Apply the change only to the page currently displayed in Acrobat.
All Pages — Apply the change to every page of the document.
Page Range — Enter a specific range of pages, such as 1-5, 3,7,12, or 1-3,8-10.

When processing multiple pages, the same page box dimensions are applied to all selected pages. This is useful for normalising page sizes across a document that contains pages of varying dimensions, which is common in documents assembled from multiple sources.

Saved Configurations

The Configuration dropdown lets you save and recall named presets. This is valuable when you regularly apply the same page size settings — for example, always setting the trim box and bleed box for A4 with 3mm bleed in your prepress workflow.

To save a configuration, set all options as desired, type a name in the configuration dropdown, and click Save. To recall a saved configuration, select it from the dropdown. To remove a saved configuration, select it and click Remove.

Configurations are stored in the MediaSizer.ini file in your local application data folder and persist between Acrobat sessions. Each configuration stores the selected page boxes, size, orientation, scaling option, measurement unit, and page selection.

System Requirements

Adobe Acrobat: Acrobat Pro or Standard DC (2017 or later). Not compatible with Adobe Acrobat Reader.
Operating System: Windows 10 or Windows 11 (both 32-bit and 64-bit Acrobat installations are supported).

Support

If you encounter a problem or have a question not covered here, please get in touch: