MaskIt

User Guide — Mapsoft MaskIt Plugin for Adobe Acrobat

Overview

MaskIt is an Adobe Acrobat plug-in that masks (hides or removes) rectangular areas of PDF pages. By specifying distances from the left, right, top, and bottom edges of the page, you define a rectangular boundary. MaskIt then either masks the content inside that rectangle (removing the selected area) or masks the content outside the rectangle (keeping only the selected area and removing everything else).

This is particularly useful for removing headers, footers, margins, barcodes, confidential information, or any other content that occupies a consistent rectangular region across one or more pages. Unlike Acrobat's built-in crop tool, MaskIt can permanently erase the masked content from the PDF rather than simply hiding it behind a crop box.

MaskIt also supports an interactive tool mode where you can draw a mask rectangle directly on the page in Acrobat, and the boundary values are automatically populated in the dialog. The plug-in includes options for handling rotated pages and can process individual pages, page ranges, or entire documents.

Getting Started

After installation, MaskIt adds a menu item under Extensions › Mapsoft › MaskIt in Adobe Acrobat. Click this to open the MaskIt dialog. You can also use the MaskIt toolbar tool to draw a mask rectangle directly on the page before the dialog opens.

Open a PDF document in Adobe Acrobat.
Go to Extensions › Mapsoft › MaskIt.
Enter the boundary distances (left, right, top, bottom) for the mask area.
Choose the mask type: Inside or Outside.
Select which pages to process.
Click OK to apply the mask.

Tip: If you use the MaskIt toolbar tool to draw a rectangle on the page, the left, right, top, and bottom values are pre-filled from your selection. This is the quickest way to define a mask area visually.

Defining the Mask Area

The mask area is defined by four boundary distances measured from the edges of the page:

Boundary	Measured From	Description
Left	Left edge of the page	The distance from the left edge of the page to the left side of the mask rectangle.
Right	Right edge of the page	The distance from the right edge of the page to the right side of the mask rectangle.
Top	Top edge of the page	The distance from the top edge of the page to the top side of the mask rectangle.
Bottom	Bottom edge of the page	The distance from the bottom edge of the page to the bottom side of the mask rectangle.

Together these four values define a rectangle on the page. For example, setting Left to 25mm, Right to 25mm, Top to 50mm, and Bottom to 20mm on an A4 page would define a rectangle inset by those margins from each edge. The preview area in the dialog updates as you change the values so you can see the mask area before applying.

All four values must be non-negative, and the left + right values combined must be less than the page width (similarly, top + bottom must be less than the page height). If the values define an invalid rectangle, MaskIt will display a warning.

Mask Type

MaskIt provides two masking modes that determine which content is removed:

Inside

When set to Inside, MaskIt removes the content within the defined rectangle and leaves the surrounding content intact. Use this mode to remove a specific area of the page, such as a letterhead, a barcode, or a block of confidential text.

Outside

When set to Outside, MaskIt removes all content outside the defined rectangle and keeps only the content within it. This effectively crops the visible content to the specified area. Use this mode when you want to extract or isolate a specific region of the page.

Permanent Erase

MaskIt also provides an option for permanent erasure. When this option is enabled, the masked content is physically removed from the PDF file rather than simply being hidden. This is important for redaction-style workflows where sensitive information must not be recoverable from the file, even by advanced PDF editing tools.

Allow for Rotations

Enable the Allow for Rotations option when working with documents that contain pages with different rotation values. When enabled, MaskIt adjusts the mask boundaries to account for the page's rotation attribute, ensuring the mask is applied to the correct physical area regardless of how the page is rotated in the PDF.

Measurement Units

The Units dropdown lets you choose your preferred measurement unit for the boundary values. Available units include:

Points — The native PDF unit (1 point = 1/72 inch).
Millimetres — Metric measurement.
Centimetres — Metric measurement.
Inches — Imperial measurement.

When you change the unit, all four boundary values are automatically converted to the new unit. Your preferred unit is remembered between sessions so you do not need to change it each time you open the dialog.

Page Selection

MaskIt provides flexible page selection for applying the mask to specific pages within the document:

Current Page — Apply the mask only to the page currently displayed in Acrobat. This is selected by default when the dialog opens.
All Pages — Apply the mask 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.

You can also restrict the mask to odd pages only, even pages only, or both odd and even pages within the selected range. This is useful for duplex documents where headers or footers differ between left and right pages.

Saved Configurations

The Configuration dropdown lets you save and recall named mask presets. This is valuable when you regularly apply the same mask to documents with a consistent layout — for example, always removing a 15mm header area from scanned documents.

To save a configuration, set the boundary values, mask type, and page selection 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 MaskIt.ini file in your local application data folder and persist between Acrobat sessions. Each configuration stores all dialog settings including boundary values, mask type, page selection, and the selected measurement unit.

Tip: Create named configurations for different document types in your workflow. For example, “Remove Letterhead”, “Crop to Content Area”, or “Remove Footer Bar”. This saves time when processing similar documents.

COM Automation

MaskIt provides a COM automation interface (IMaskItAuto) that allows external applications and scripts to apply masks programmatically. The COM object exposes properties for the left, right, top, and bottom boundary values, the mask type, and page selection, along with a Mask() method that applies the configured mask to a PDF document handle.

This interface enables integration with automated document processing pipelines, batch scripting, and custom applications. You can call the automation interface from any COM-compatible language, including VBScript, PowerShell, C#, and Python. The automation DLL (MAPSMaskIt.dll) must be registered on the system before use.

MaskIt also exports a standard Mapsoft batch HFT (Host Function Table), allowing it to be driven by the Mapsoft Acrobatch plug-in or other Mapsoft plug-ins that support inter-plugin batch communication. This enables MaskIt to participate in multi-step batch workflows alongside other Mapsoft tools.

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: