Go ahead and graft your pear as soon as the leaves are the size of your little fingernail, or the size of a squirrel's ear. Use dormant scions.

Yes, that. But if delayed you can graft even later if the scion is dormant, or just barely breaking dormancy.

Yup, what he said- but, a big but: the less dormant the scion the more likely that the graft will fail. And even if the scion is not dormant you may be able to get the scion to stick to the stock without expressing, or it may express and have the buds wither. As long as the scion itself does not dessicate I would leave it in; you may have a bud emerge the next year.

You may be able to get a reluctant bud to sprout by scoring the wood above the branch to which you are grafting. So say you have a half-inch diameter branch and you have stuck a scion onto it. Just above where the half-inch branch attaches to the trunk you can take your pocket knife or pruning saw and cut a groove through the bark right down to the raw wood of the trunk. (Don't cut into the wood itself- just cut through enough to remove a strip of bark down to the wood.) That'll limit the amount of hormone that the tree drips down to the branch to limit competition.

If that doesn't make sense please say so and I'll try to restate it.

Good luck and keep at it.

This is a little different method that I mostly use with grafting pears and I normally get a high percentage of takes. Anytime from January 1-February 15, I whip graft with electrical tape. Make sure to not let the cut to the stock tree and scion dry out. The new grafts will normally start growing about 1-3 weeks after the stock plant does. This method is not perfect but I get good results. It is better to graft early, rather than waiting to near leaf out time. With this procedure if you wait to near leafing, your failure rate will increase. This is simple and easy with a wide range of time to get the grafts in place. Good luck, Bill