Another question entered into Google and landed here: "How much can a cobbler stretch a pair of boots?"
Good question. The answer to this question depends on what the boots are made of.
If boots are made of regular leather, then you need to know if the boots are lined with leather.
If boots are leather lined, a cobbler can usually stretch the shafts up to 3/8 inch (1cm) in additional overall circumference (which for those who are not math-inclined, is not the same as the diameter. Boot circumference is the distance around the inside of the boot shaft).
If the boots are not lined with leather, then the boot shaft can possibly be stretched even a little more, up to about 1/2 inch (1.3cm) if the cobbler takes his time and uses specialized equipment.
If the boot shaft is made from materials other than leather, like "Dehcord" (which is the synthetic product from which the shafts of stock Dehner boots are made), then it cannot be stretched. Attempting to stretch synthetic materials causes breaks in chemical bonds that form the product -- what results is cracking and visible breaks in the surface of the boot. It ruins it.
Boots that are made of leather but coated with a plastic top coat, like Chippewa Hi-Shine boots, Chippewa Trooper Boots, Intapol Patrol Boots, or All American Patrol Boots, also will develop surface cracks if they are stretched, so it is not recommended to try to have those boots stretched.
If you need the foot of the boot stretched, that is possible, too, with the right equipment. A cobbler has a device that can apply pressure from inside the boot's foot to stretch it. The amount of stretching that a cobbler can do for a pair of all-leather boots is about one width size wider (such as from a "D" to an "E".) However, no boot can be stretched longer, such as from a size 10 to a size 10.5.
How does one find a cobbler with the correct equipment to stretch boots? While the Yellow Pages (business telephone directory) is quickly dying, if you have one, you probably can find a listing for a cobbler in it. You can also use an internet search engine to find a cobbler on-line. Consider additional search terms of "shoe repair" or "luggage repair" as well. Most shoe and luggage repair shops have the equipment to stretch boots.
And for the do-it-yourselfers, there are various methods described on the internet about how to stretch boots. Some of the ideas work (more-or-less) and some do not. For more details on how to do it yourself, See this article on the Boots Wiki.
A word of advice to the DIY types: do NOT be fooled into buying "boot stretching liquid." This stuff is isopropyl (rubbing) alcohol. No need to buy a product that has a label that proclaims magical results, when it actually is exactly the same stuff that you can find in any drug store for one-sixth the price. Just go to a drug store and buy a bottle of regular rubbing alcohol -- then be sure to follow the instructions referenced on the Boots Wiki on how to use it.
Life is short: get your boots to fit!