My pertinent experience for this blog post is with an iPad (specifically a "the new iPad" which is generally referred to as the iPad 3) but I expect that these same results would be experienced for any iOS device (iPhone, iPod Touch, etc.). No matter what your device, if you have direct experience with using this technique with a device that is slow, unresponsive, and/or crashing, please post a comment about your experience (whether or not it helped, anything you did different, etc..) as that will very much help other readers.

My iPad had become very unreliable: it crashed (or perhaps I should say it spontaneously rebooted) regularly and when it was running, it was very slow to respond and at times downright unresponsive. The condition got worse and worse to the point where I simply couldn't use it because it just wouldn't respond for more than a few seconds before automatically restarting of its own accord.

The good news is that I was able to get my iPad back working like new by restoring it from a backup; the bad news is that by the time I tried this approach, it had become very hard because the first step in the process is to do a full backup of the device and that was very, very difficult because of my iPad's propensity for spontaneous reboots (but fortunately, with a lot of patience and persistence, I was able to get my iPad to backup).

Now, to be clear, when the iPad was merely painfully slow, I had considering doing a restore from a backup but, though it's easy and straightforward enough, doing a restore from a backup does take a bit of time and so I was reticent to do it without some indication that it might help. For that reason, I searched for guidance and I wasn't seeing people prominently pointing to doing a restore from backup as a troubleshooting step to try and so I didn't jump to do it; as I said already, that that proved costly because things go so bad that I almost couldn't successfully backup the iPad. And that then is the reason I'm writing this post: my hope is that when others search in the future for what to do about extremely slow-to-respond (and even entirely unresponsive) iPads, iPhones, and iPod Touches that crash and/or spontaneously and automatically reboot, they'll find this blog post and be encouraged to try restoring from a backup--and then of course I further hope that those who do try this approach will get the same results that I did: iOS devices that work like new. Please let me know in a comment if it does or doesn't work for you.

Now as to the process of doing a backup and restore: I won't get terribly detailed here because you can find the key details on Apple's Support website. But some notes:

1. As I mentioned, this process is easy and straightforward but it does take some time; accordingly, make sure you'll be able to dedicate your device to this task for an extended period of time (in other words, don't expect to start this and be able to then take your iPhone somewhere a half hour later).
2. To do the backup and restore, I used iTunes, not iCloud and I recommend that you do the same as it will certainly be faster. However, I don't know any reason that it wouldn't work using iCloud.
3. Since what you're going to be doing is reinitializing your device from a backup, the first thing you need to do is backup your device so that the backup you're using for the reinitialization is current.
4. Then you need to erase your device; this is mentioned but not actually described in the link above. You can do this via iTunes or you can do it directly on the device. I believe these are not entirely equivalent approaches but rather a factory reset via iTunes is a more extensive reset than merely erasing the content and settings directly on the device. I erased the content and settings directly on the device and that worked great for me. Note that the information on erasing the content and settings directly on the device does not mention turning off Find My iPad (or Find my iPhone or whatever is appropriate for your device) but to keep yourself out of trouble, I recommend turning that setting off. I turned it off prior to doing the backup (step 2 above) so that Find My iPad was completely out of the picture and couldn't cause any issues.
5. Once your device has been erased/reset, you need to restore it from your backup. This part will take the longest. Fortunately, you can just let it run while you do other things.
6. Once you've restored the backup, if all goes well, you should hopefully be in really good shape with your device! Specifically, your device should work like new. If it doesn't then unfortunately, you are probably dealing with issues that this approach won't fix. But if your device is working well at this point, you'll want to go back and turn on Find My iPad (or Find my iPhone or whatever is appropriate for your device). In addition, if you're an iCloud Keychain user, check the iCloud Keychain setting (it's on the same screen as the Find My iPad setting): I found that it was off and needed to be turned on (but fortunately, so far that's the only setting I've found unexpectedly changed during this process).

So what exactly was wrong with my iPad that the backup and restore appears to have rectified? Well, I had thought all the issues I was seeing (in addition to the poor performance and reliability, I had one app update that just wouldn't finish, leaving the app in a sort of state of limbo; I couldn't remove it by clicking and holding and hitting the "x" to delete it, I had to delete it via the Manage Storage area of the Usage area of the General area of the Settings app) were perhaps because some of my iPad's solid state storage had gone bad (and I was hoping that upon the backup and restore, iOS would avoid using the bad parts of the storage) but after the restore I noticed that my iPad gained around 3 GB of additional free space. Interestingly, when my iPad was misbehaving so badly, the amount of free space reported for the iPad in iTunes did not match the amount of free space reported by the iPhone itself; however, after the backup and restore, the 2 reports matched. I checked my iPhone, which doesn't have performance issues, and the report of its free space in iTunes matches what the iPhone itself reports. This all leads me to believe that mismatches (at least significant mismatches) between the reports of the free space provided by an iOS device and iTunes may be a good indicator that something is seriously amiss with that iOS device. Certainly in the case of my iPad it seems there were some serious "cobwebs" in there that were cleared out by the backup and restore. But regardless of exactly what was going on, I'm just glad it seems to be better now and I hope it stays that way!

As they say, your mileage may vary but I very much hope your results are as good as mine have been!

To give credit where credit is due: I became aware of this technique in the post at https://productforums.google.com/forum/#!topic/docs/m-hUu90ZGI0.

Google Docs is wonderful in many ways, however, there are a couple of areas where it has limited functionality that were issues for me recently and this is the first of a two-part series of blog posts (see the second part here) on what I did to work around those limitations.

Google Docs only allows you to create documents from a set of standard page sizes; it does not allow you to create a document of a non-standard page size (custom page size) of your choosing. Fortunately, there is a workaround that will allow you to create a document of any page size. If you're printing (in my case, I was printing envelopes), working from a document that properly represents the size of your print media is at the very least helpful, if not downright critical.

The workaround is to create a document outside Google Docs (yeah, that's bad but it's what you have to do) with the proper page size (and get your margins like you want them as well because if you try to change those in Google Docs, you'll also be forced to change the page size at the same time and of course you'll be forced to change the page size to one of the standard sizes). I had success uploading a Word-type document (both .doc and .docx worked for me) but not uploading a PDF or a Pages-type document. Note, however, if you don't have Word on your machine, you can get OpenOffice for free. In addition, if you have Pages, you can create the document there and export it as a Word-type document and that works (in fact, that's what I did; for more on how to do it, see this associated post of mine).

One special note here: I encountered a bit of a strange issue with pages with a width of 7.25" (my custom size also had a height of 5.25" but I didn't investigate whether or not that was relevant to the issue). The issue was that Google Docs for some reason was inserting a blank page between every actual page on print/download. Very weird stuff. By using a document with a width of 7.75" with an additional .25" margin on left and right, Google Docs did not insert that extra blank page and for my situation, this was a suitable workaround because what I needed to be able to do was print and on my Mac, the key for printing was the center of the content (if in your situation, you ever see an issue like this but the key for printing is the left of the content then add additional width to the page and instead of dividing the additional width evenly between the left and right margin, just add all the additional width to the right margin).