From time to time we are sent scans of printed documents and asked to make changes. This may seem like a simple thing to do, but it can actually be quite challenging. Even changing a phone number can lead to a great deal of work and take many hours depending on what is provided.
Here's an example of an order we received recently that will help me illustrate this point.
This is the front side of the postcard (I blacked out the company details)
This is the back of the same postcard
The customer brought this postcard to our client's store and asked that the coupons be removed. So the associate crossed out those areas and scanned them and sent them to us. In this case, removing the coupons isn't too difficult, especially on the back. The problem is that there is a dot pattern on the text and the photos, which will not produce a good quality print. Scanning a printed design and printing it again reduces the quality level. It's what's known as a second-generation print and should be avoided whenever possible. You can see the dot pattern in the close-up and also a hair on the top right.
There are several ways to deal with this. The text can be retouched out of the scanned postcard and retyped or better yet, the entire postcard could be recreated from scratch using similar stock photos. If only the text is replaced, there will still be a dot pattern on the photos and therefore a quality loss. There are tools in Photoshop that will decrease the dot pattern somewhat—the Despeckle and Dust & Scratches filters work best. However they also cause a loss in sharpness so it's a trade-off. This also still results in the print being second-generation, not the same quality level as the original.
If a customer presents you with a project like this, be sure to help them understand the challenges with getting a clear print from a second-generation scan. The best option may be to have the document recreated which means it won't match the original exactly, but it also will ensure the best possible printed piece. Most customers will appreciate being given this information, because their marketing materials are what their potential customers will use to form an initial impression.