Let's see if I can answer some of your questions...
Fruits tend to be high acid so already low risk and the sugar acts as a preservative as well. They are also boiled so bacteria is killed there.
Pectin and sugar combine to create the "jell".

You can add dry spices to nearly any recipe. Fresh herbs are not allowed unless substituted (not added) for another low acid ingredient (i.e reduce the amount of bell peppers in salsa to add more cilantro).
Yes, you can put cloves or cinnamon sticks in the jar with your jam, but they can be awfully strong, so go easy! Or, just cook your jam with the spices in a bag and remove spices before canning.

Make sure to follow "approved" recipes. You can always check here if you question them. There are lots out there that aren't approved. Many people still use old methods that current science has proven to be unsafe. Why risk it?

And...........
Welcome to our little group of addicts!! Post often, we don't mind questions at all! There is a search engine and lots of information there, so be sure to try that. I find that just one word in the search field yields more results. Yes, you're going to have to sort through more, but it won't eliminate pertinent info.

My name is Deanna and I'm addicted to Food Preservation...

Hi Paulina - the only thing I can think of to add to Deanna's info is that yes, you can reduce somewhat the amount of sugar in jam and jelly but you risk it not setting when you do and there are limits. Takes some experimentation and it is easier to use the approved sugar-free or low sugar recipes if needed or use more pectin.

Are jams preserved based on the acidity of the fruits, much like tomatoes, and not by the sugar or pectin?

To clarify 1 point, jams and jellies are preserved based on the acidity of the fruit and sometimes the added acid (usually lemon juice) when it is called for as it is in many jelly/jam recipes.

But do not equate fruits with tomatoes. Tomatoes are considered low-acid and additional acid in the form of bottled lemon juice is required when canning them.

Might I suggest you check out all the great Intro to Canning and the Canning FAQ's supplied by NCHFP. I have linked them below. And the FAQ are linked in the index on the L side. They cover most all the basic questions with lots of good detailed explanations.

Welcome! ;)

Dave

Here is a link that might be useful: General Canning Intro

Using regular pectin in jams and jellys require exact measurments of sugar. If you prefer less, or none, you can either use the Pomona pectin, or one of the low sugar types. These same questions were recently posted here too.. Usually, no whole spices should be added. Think of cinnamon as being wood bark, which can leave a lot of unpleasent taste, same with whole cloves. Both can be overpowering when added to canning. Sugar reduction will reduce chances of the jelly or jam from setting up, unless you use pectin products that set up without little or no sugar, you will not usually have a good set. I like adding additional acid blend to my jams and jellies as it helps give them more 'character', malic, citric, and tarteric acid are used to acidify wines, and work very well in keeping qualities of jams with low or no sugar added.

I tucked a cinnamon stick and a few cloves into 1 jar of pears just to see what it will taste like. We probably won't open the jar for a while; I will report back this winter to let you know what happens!

I use the powdered cinnamon now. I feel it gives me better control of the flavor when I can pears.

Doesn't the powdered cinnamon leave "silt" in the jar?

Re: sugar in canned fruit. That's mostly for flavor, and we like ours pretty natural. We add the juice to tea or to other fruit juices, or even just pour it in a glass and drink it, so the syrup is extremely light. Could be eliminated altogether and just can in water and natural juices, but remember that the lighter the syrup, the greater the tendency for the fruit to "float". Just aesthetic.