how to remove black background from a picture?

Actually the answer is Adobe Acrobat Pro to edit a pdf document like a string of texts downloaded from Apple Messages.  The Adobe product has the "PDF Editing" Tool in it.  How do I know, because I ended up buying Illustrator, contacting Adobe for help in how I do that - because on opening it I was confronted with a foreign language of commands, drop-down menus.  I am NOT a literate computer user, and I have learned a valuable lesson through this process, and that is that whenever:  1) someone says it can be done with "xyz",  unless they have actually done it and can clearly explain how, and, that;   2) when someone says "Oh it's straightforward, just do xyz", run for the hills!!!  Because it isn't.  

I tried to use the robot AI thingy at the bottom right of the Adoobe help section that took me some time to find, and the person who shall remain nameless (in India) was curt, expected me to know how to use the tool and he was just therer to just tell me if I was right or wrong.  He dropped my string of queries and never came back.  So much for customer service thru this way of communicating.  I found a number for Illustrator and after many long waits and re-dials found a support person who did his darndest to help me but could not.  At the end after  many long (obvious) consultations with senior people told me that this was the wrong tool to use.  I guess I will not get my money back for that.  I had to use Adobe  Acrobat Pro (apparently the full user tool if you want to or have to create these documents, and as Apple can download the Message string into a number of options like pdf), and so removing the black layers over the images on the pdf download could be done in that.  He guided me to obtain Pro.  I then asked to talk with a senior person who could help me. I was told I would have to make an appointment and that the person would call between 8:30 AM PST and 11:00 PM PST.  I said that is ridiculous and finally had it down to a 30  minute window.   This person who finally called me (from India) was really good - he spent 2 1/2 hours trying different things with a sample file I put together (yes, I can send a text...).  Finally he gave me instructions on what each step should be.  Of course the first time that I used it on the PDF document (CLICK ON PDF EDIT IN THE RIGHT HAND MENU) just 10 minutes ago, it did not work as his model did!   *&$%@!?!@!!~!!!!!.  Now what...?  Call back I guess.  But it is clearly the right tool - when he dialed in to take over the screen and get familiar with the problem, he used this product and finally tested it using the  method he developed.  So darn easy once I watched and took notes...!