I have lots of songs scanned into my "Google Drive". You can get a small cloud based storage solution for free from several places online. Dropbox, Google, Apple, if you have an iPhone/iPad. They all charge more if you grow to need more space, but if all you do is put .PDFs on your drive accout, you probably won't be out of room very soon.
If you are scanning, there is a little tool that I use to make PDFs smaller:
Compress PDF Files with NXPowerLite | Neuxpower
Not necessarily to save space, although it does do that. I like to make my PDFs as small as possible so they load up faster on my pad.
If it's an older ipad like mine, it probably has wi-fi only capability. Be aware, that if you do go to a cloud-based storage solution, you won't have access to all your stuff unless there is wi-fi where you are located. You can download a .pdf reader that will put what you select on on your pad so you can access it whether you have wi-fi or not, so be sure to get one of those. Watch for capability to do on-screen editing. If you find the right one, you can use your finger, or a pad-compatible stylus to make notes right on the .PDF.
Another thing that may prove helpful is using your phone as a "hot spot". My phone carrier includes this feature with my cell plan, so I can just make my iPhone the wi-fi when I need it. I never leave this feature on because skeve-bags will hack your phone in public places if you leave that vulnerability open to them. I just turn on the phone's hot spot feature, do what I need to do and then turn it back off again. It's more convenient than tracking down the wi-fi password to the place where you are....
Last thing, I know nothing about, but there is plenty of info here on TB, is page turners. If you want to be super fancy, you can get one of those that will connect a page turning foot pedal to the your pads bluetooth. Page forward and back by pressing a forward or back pedal.
I don't actually use any of this stuff, am a paper-pencil-highlighter kinda guy. I know most of what I just posted because I just know it. A couple of things I am passing on just what I have read here on TB... Hopefully this helps you!!