HOW DO I?

Export a grid to a full featured graphics app like Graphic for iPad

Built-in Paint tools can be used to color and annotate the grid, however, some projects require more powerful tools.

Use any drawing app that can import and edit a PDF
A full-fledged graphic design program will give you more capabilities than the built-in paint tools. One app we like and use is Graphic for iPad. [Graphic is also available for the Apple Mac] It has an amazing amount of power for not much money and also works with an Apple Pencil. Graphic for iPad can add lines, notes or even modify the shapes originally created in our app, for example, and even change line color or width.

Coloring and editing a grid using Graphic for iPad

NOTE:  We have no association with Graphic other than we use it

When you export a PDF to Graphic, have Graphic “Import as Vector Objects”. Now you can add lines/text on top, and you have access to all the lines in the drawing.

So, for example, in this image, you can grab a section of the grid and change the colors of the lines in that section. Or change line weights, add arrows or dashes, even grab and move things around on the page.

Another helpful feature is to place “Smart Guides” on the paper's grid lines. This will force edits to snap to the paper's grid rather than Graphic’s internal grid points. This should make it easier to draw on your own lines, particularly with an Apple pencil.