I have an iPad iOS 5.1.1 and need a PDF reader is that possible??

What I do is look through the pdf apps in the app store. I look for one that have a change history for the time frame you need the app. That is when did ios 5.1.1 come out? Answer: iPad, and iPad 2 on October 12, 2011

https://en.wikipedia.org/wiki/IOS_version_history#iOS_5

You can install itunes on a mac or pc. Logon to itunes store with the apple id you use on your ipad. Download the apps you need. Now, you to your ipad. look in purchase history. down load the apps you want. For older apps, you will get a question "do you want to use an older version?" Say yes.

I do not know if any of these apps work on 5.1.1, but they have been around for awhile.

PDF readers and Presentation software

GoodReader

-- With GoodReader on your iPad/iPhone, you can read virtually anything, anywhere: books, movies, maps, pictures.

-- sync with Dropbox, OneDrive, SugarSync and any WebDAV, AFP, SMB, FTP or SFTP server

-- The types of annotations that can be created and edited in GoodReader include typewriter text boxes, popup comments ("sticky notes"), text highlights, freehand drawings, lines, arrows, rectangles, ovals, cloudy shapes, text underlines, strikeouts, text insertion marks.

-- GoodReader® is the super-robust PDF reader for iPad, iPhone and iPod touch. Its iPad version was the #1 selling non-Apple app for iPad in 2010 in the USA, and all those years we've been adding new features, keeping it the best mobile productivity tool on the market. And we've got a lot more to come!

http://www.goodiware.com/

PDF Expert – the PDF handling app for the iPad. "It allows you to markup documents with highlights and handwriting, insert text and stamps, sign and even merge PDFs."

https://itunes.apple.com/us/app/pdf-expert-5-fill-forms-annotate/id743974925?mt= 8

iAnnotate – turns your tablet into a world-class productivity tool for reading, marking up, and sharing PDFs, Word documents, PowerPoint files, and images. Has a secure document edition designed for corporations.

http://www.branchfire.com/iannotate/

Documents 5
"Read, listen, view, annotate almost anything you want on your iPad and iPhone. Files, documents, books, any content is at home in Documents by Readdle."

"Copy Documents from Mac or PC"https://itunes.apple.com/us/app/documents-5-file-manager-pdf-reader-and-browser/ id364901807?mt=8

Folder Plus

a file and folder manager

https://itunes.apple.com/us/app/file-manager-folder-plus/id484856077?mt=8

iPresent

"iPresent is a highly polished and interactive content distribution platform. ...

• Present PowerPoint, PDF, Video, HTML5 and many more resources on mobile devices
• Ensure everyone always has the most up-to-date content"

http://www.ipresent.com/Features

I've used GoodReader for years...and had it back when I was on ios 5, so I'm sure it will work if you find the correct version to install. GoodReader's current version is $4.99. The newest version uses a blue icon, the version I think you need has a green icon.

This is probably one of the best apps I have. I use it almost daily as a file manager for ios. You can do a lot of things like annotate PDF's and store them in iCloud so they are accessible on all devices. Here's a link to GoodReader's website:

GoodReader

iBooks also lets you read PDF's but getting one into iBooks is tricky if you already have it. If you downloaded it online and can get to that page again you can use the Share icon to save it in iBooks. iBooks isn't great for sharing PDF's across devices though. Generally you'll on have access to a PDF on the device you downloaded it too, and if you restore that device there's a good chance your PDF's will all disappear unless you've taken extra steps to save them somewhere first.

You can see which apps are still compatible with iOS 5.1.1 here: Finding iOS Apps Compatible with Older Devices

You could also try downloading an older version of a PDF reader app if the current one requires a newer iOS version: App Store: Downloading Older Versions of Apps.

(Note that I may receive some form of compensation, financial or otherwise, from my recommendation or link, because some pages on the site contain small banner ads).