How can I get an older version of Adobe PDF reader for iPad 2?

Search for “PDF” using the Search tool within the Apple App Store App. For each App in the list, check for compatibility with iOS9.

Be aware that iPad2 is, to all intents, obsolete - and 32-bit Apps are becoming very difficult to find. Here is one App that claims to still support iOS9 - but if you look, you may find others...

https://apps.apple.com/gb/app/pdf-reader-document-expert/id422798908

PDF Reader Pro Lite version or Pro

https://apps.apple.com/us/app/pdf-reader-pro-lite-edition/id919472509

https://apps.apple.com/us/app/pdf-reader-pro-sign-edit-pdf/id883101890

GoodReader

https://apps.apple.com/us/app/goodreader-pdf-editor-viewer/id777310222

GoodReader is the Swiss Army knife for any kind of document.

There maybe a few others.

There are virtually NO MORE older, legacy, popular, third party apps for old 8 and 9-year old iPad models, any longer, from the Apple iOS App Store.

Many, MANY third party app developers have, permanently and forever, removed all their older, legacy apps from Apple's iOS App Store servers!

These old 8 and 9-year old are very soon going to be fully and completely obsolete by the end of 2020.

If you wish to keep using this over 9-year old iPad and keep the apps you have on this device.

Tap and read my entire link below for further information and instructions.

If you own OLD 8 and 9 Year Old iPad mo… - Apple Community

Best of Luck to You!

iPad2, iPad3 or original iPad mini cannot be updated beyond iOS 9.3.5 (WiFi Only models) or iOS 9.3.6 (WiFi & Cellular).

Apple ended update support for these devices in September 2016. None of these models can be updated to iOS 10 or later versions, as the internal hardware does not meet the minimum technical requirements for new versions of iOS/iPadOS.

Many App Developers have also dropped support for older devices and iOS versions preceding iOS11/12/13 - and have withdrawn older versions of their Apps from the Apple App Store, now limiting utility and usefulness of older devices.  Once older App versions are withdrawn, they cannot be (re)downloaded or (re)installed.

If Apps that you need to use now have higher minimum iOS-version requirements, your only option is to replace your iPad with newer model.

I hope this information is helpful - if only in making clear the limitations of your current iPad and your options.

The ability to get an older version of an app is up to the app developer. They determine what they will keep available in the App Store. If you cannot get an older version from the App Store, check with the developer and see what they say. However, I would not expect much. Developers are not supporting the 32-bit versions of apps any longer. It is what it is now.

To reiterate, once older App versions are withdrawn from the App Store, they cannot be (re)downloaded or (re)installed on your device.

The only source of App for iPadOS/iOS is the Apple App Store. There is no alternative source.