Addressing your principal difficulties with charging your iPad, these support pages should help with troubleshooting battery and charging issues:
Charge and monitor the iPad battery - Apple Support
If your iPad won't charge – Apple Support
Your iPad combines both the charging indicator and battery status within a single icon that you will see at top-right of the iPad screen - this only being visible when the iPad and screen are powered-on.
Troubleshooting generally requires substitution of the Power Adapter and cable for another known-good item. Most models of iPad require a Power Adapter rated at 12W (i.e., 2.4A @5V) or greater to reliably charge. 5W Power Adapters (1.0A @5V) intended for older models of iPhone are inadequate to charge an iPad; if the iPad charges at all, charging will be very slow. Recent models of iPad are supplied with a 20W USB-C Power Adapter.
Some third-party USB-C power adapters (and portable PowerBanks) may not support USB PD (Power Delivery). Power Delivery mutually negotiates the charging voltage; the source, load and cable are all elements involved in the negotiation protocol. Unless the Power Adapter explicitly supports USB PD, it will almost certainly fail to charge the iPad; proprietary charging standards, such as QC (Quick Charge), are not supported.
Be aware that many computer USB ports also cannot source sufficient power to charge an iPad. Unless explicitly designed for charging connected devices, computer USB ports are typically limited to 0.5-1A @5V (i.e., 2.5-5.0W).
If you continue to experience difficulties when using an appropriate Power Adapter of 12W or greater, you might be best advised to seek assistance directly from from Apple Support. You can contact the Support Team using the Support link at top-right or bottom-left of this page. Alternatively, you can initiate and manage your support cases from Apple devices using the excellent Apple Support App. If not already installed, the App can be downloaded from the App Store:
https://apps.apple.com/app/apple-support/id1130498044
You might also visit the Genius Bar at your local Apple Store or Apple Authorised Service Provider (AASP) - where the technicians will be able to test and assess your iPad, Power Adapter and cable(s):
Genius Bar Reservation and Apple Support Options - Apple
User Guide
As for the User Guide, Apple does not supply a printed User Guide with its devices. However, Apple does offer a comprehensive online User Guide for iPadOS 17 (and earlier versions) that can be accessed using a web-browser:
iPad User Guide - Apple Support
The Tips App, installed by default on new devices, does eventually lead you to this resource. If not installed, or deleted from your iPad, the Tips App can be reinstalled from the App Store:
https://apps.apple.com/app/tips/id1069509450
While previous major versions of iPadOS also had a downloadable User Guide that could be accessed using the Apple Books App, for some inexplicable reason Apple has not produced a downloadable Guide for iOS/iPadOS/tvOS 17 - or recent versions of macOS.
Hopefully Apple will address this significant omission - as many Users have cause to seek information from the User Guide when either offline - or when attempting to resolve an issue that may, until resolved, prevent access to online resources. If you have any comments this regard, Apple invites submission of comments and feature requests via its Product Feedback portal. For iPad and iPadOS:
Feedback - iPad - Apple
