Q:

How do you say marketing words - lead conversion, upsell, churn reduction?

The customer lifecycle can be described as:

acquisition
lead conversion
upsell
cross-sell
churn reduction (aka retention)

How would you translate these as a businessperson?

adquisición
conversión de candidatos (really, "candidatos"?)
venta adicional (seems wrong)
venta cruzada (seems wrong)
retención (but it would be cool if there was a word for "churn")

A:

I'm not a businessperson, but here's what I found:

Most of the marketing articles and blogs in Spanish, as well as other sources I checked (like Wikipedia), seem to agree in translating acquisition as adquisición, conversion as conversión, and retention as retención. No surprise here. Just drop the "candidatos" if you don't like it (might be redundant anyways).
Upsell o up-sell:

Some sources translate it as "venta adicional". Seems to be the most used translation.
Others use the term "sobreventa". This last term is already being used for overselling, though, so I wouldn't pick it if I had to choose.
Several sources just use the English term, "upsell", sometimes even as a noun.

Cross-sell: near-unanimity once again, with everybody using the term "venta cruzada", as seen in the linked references for upsell. Wikipedia uses this term too (you can switch languages and see how they are the same concept).
Churn reduction: here "churn" is just short for "churn rate", which in Spanish is usually translated as "tasa de cancelación" or "tasa de abandono" (see Wikipedia once again, and some other sources). So when talking about "churn (rate) reduction" you can just say "reducción del (o de la tasa de) abandono" if you want to go full Spanish, or leave "churn" as-is as some do.

