OT: Technical illustrations - Outlining a line drawing

[Writer]

I apologize for the OT nature of this question, but I wasn't sure where else to ask this question.

I have some line drawings of our product to include in a small hardware guide. I want to outline the illustrations in a heavier line, but I don't know how to do it in a simple, efficient, competent way. Are there any tech illustrators here who are willing to let me in on their secret? I have access to Adobe Illustrator, Adobe Photoshop, and Corel Paintshop Pro.

Thank you for your indulgence,

Nadine