Carbs and fiber content are usually listed on package labels. If you are reading a package label it isn't paleo.
That's a bit purist, I quite often have to buy packaged products (cured meats etc.,) due to my financial situation and location at a given time. And when I do I go for what has the least additives and the least carb value.
But worrying about net carbs versus total carbs is Atkins purist not paleo. Cured meats etc., usually have only a few carbs like 2 or 3 grams and if they have fiber it is 1 or 2 grams. Not that big of a deal.
Typical non paleo 'low carb' products is where net carbs matter. I've seen low carb tortillas that show:
Total Carbs 15g
Fiber 13g
They put right on the front of the package: "Only 2 grams* of carbs." The asterisk next to the fine print then shows net carbs after subtracting fiber.
On paleo you might eat a cup of whole raw strawberries and count 11 grams of carbs and not worry about the 2.9 grams of fiber listed by the USDA. On paleo it doesn't matter that much if you have 60g, 72g or 95g of carbs a day if you are trying to lose weight.