If the recipe calls for processing I would do it. Processing ensures that the jars seal properly. It is usually called for when the product has been boiling for a length of time. The processing brings things up to the right temperature. In answer to your question yes they would keep if they seal right.

Jelly or jam won't set properly if you reduce the sugar. You can however use the light certo and get good results. It is a little softer than the regular one, but I for one like the spreadability better.

Recipes that don't call for processing are considered unsafe to use. Processing, even for pickled products (unless they are fully fermented first), is required for any safe storage. Processing pints for 10 mins. is pretty much the standard recommendation. Less than 10 mins. and you will have to pre-sterilize the jars.

In pickling recipes - that is what you are asking about, right and not jelly or jam, yes, you can reduce the sugar somewhat. But do not eliminate too much or you end up with a heavily salty taste. It is the amount and ratio of vinegar that is vital for safety. You may also want to consider subbing cider vinegar for white as many feel it gives a more mellow, less sharp flavor.

Dave

ALL foods need processing if you plan to keep them on the shelf. Even jams and jellies. Otherwise you have done nothing to actually preserve that food. No molds killed, no bacteria, and all you get is a weak surface seal. It won't be a true vacuum seal.
You can cut the sugar, since sugar isn't a preservative unless in concentrations of about 50 percent or more, as in a full sugar jam recipe.
Be sure to use current, safety tested recipes for your pickles. Lots of older recipes out there and also some newer ones that do not have enough vinegar to prevent food spoilage, including botulism. Remember, cucumbers and other veggies are all low acid foods. It takes the right amount of added acid to make them safe.

Keeping the acid level high also affects safety. I don't usually add any water to my vinegar based brines.