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Text: To select text, tap in the text and drag a control point over the text you to copy, want until the text you want to copy and paste is highlighted, then release the click. You can also tap and release a single word to select it automatically.  Pictures: Long tap the picture until a menu appears. The text or image will be copied to the Clipboard (temporary storage) on your device. If it's in a different app from the one in which you're copying, open the other app. The text or image will be inserted into the document or field at the place where you put the cursor.

Summary:
Select what you want to copy: Tap Copy. Long tap on a document or field where you want to insert the text or image. Tap Paste.