What part? Press and hold on an item, select copy, start an email, then press and hold on the writing space and select paste. Or use a specific app that holds the file, docs to go, etc and use it to email the file.
The key phrase in the advice the members have shared is anything that you can copy in the clipboard...i.e. any content that you can press/hold till a copy or cut option appears. pics and texts are the obvious content but some video files can be copied and shared. You mentioned resume as well and assuming that it's in a PDF or doc format, you can copy and share it as well. But as mentioned, whatever app you're using will still offer you the option to share from within the app itself either through email, twitter, Facebook, or other social medium.
So, to make it even more clear.... to attach photo, open photo app select the share icon (rectangle with arrow) and share to email. Same for PDF and doc, from the app you are viewing the file with you can 'share" to email. PDF notes, ibooks, docs to go, pages, etc. There isn't a find/file action for iOS otherwise.