It is possible we are unconsciously sending messages with every action, messages which are unconsciously picked up by others and used in forming opinions. (Para. 4)
Meaning: We may without knowing send messages with every action and other people may also without knowing receive them and use them in forming opinions.
pick up: learn or get unconsciously and without particular effort
Children pick up foreign languages easier than adults. 孩子们学外语比成年人容易。
When I lived in China, I picked up some ideas for good cooking. 我住在中国时，学会了一些烹调知识。