Thank you so much for sharing your question with our network. I was happy to dive into this for you, and I actually found this related forum post to walk you through inserting your logo into a custom packing slip.
I recommend checking out those instructions, as they include the style class needed to customize a logo's dimensions. You will notice this style determines a logo's width and height in pixels, which can also be further customized to your own dimensions by changing the number values for each.
When you don't specify the size you need, the logo will display in its' original form.
I trust that helps, but let us know if you have more questions.
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