Earlier quoted context omitted.
In addition to the vertical whitespace, also (I feel) there's too much text there. I would just put "Headless Browser Software-as-a-Service (SaaS) that's free for light use, and cheap for heavy use." in as big a font as I can without it being annoying and move everything else lower, visible when the page is scrolled. Add a diagram if you could that supports the core product offering. Don't add carousels (please.) Lit…
Thanks for the feedback guys, the marketing+ux roles are definitely in my "fake it" category :) I will try improving this.
In between the big 3 sections, I would do at least 40px.
In terms of spacing between the heading and the content below, I generally use a variation of the rule of thirds. It's not a steadfast rule, but generally if you have 60px above a heading, something like 20px between the heading and the content it belongs to would work.
Also make your primary CTA bigger and keep it to one line. Put that 500 pages free text outside of the button:
Sign up now and get 500 pages free
[ SIGN UP NOW ]
I agree with the too much text comment as well, especially above the fold. Keep it simple and then provide a section where the users can go for more info if they need it.
Your headings and boxes are not aligned on the left side.
Change those example buttons into regular links.
40px+ between navbar and the h1, also make the h1 medium/bold weight. It looks weird when you have headings of the same font family alternate between bold/light.