Let’s start by thinking about your question. “Change the size of pictures, without losing quality”. What is quality of picture? Usually resolution and color faithfulness. Change the size? One cannot add information to an existing picture, so one cannot make it larger and not have a noticeable change in the accuracy of the image. Most programs will either dither, average to add new pixels or just pixelate and reduce resolution. So one can’t increase the size of pictures maintaining “quality”. Reduce the size? You are taking away something which contributed to the quality of the original. Something had to go. What? Different starting images formats and different adjustment mechanisms will alter differently. No pat answer there, but certainly quality lost. Putting the picture in a PDF format file and changing the image size suffers from the problems mentioned above. That doesn’t help at all. The Windows Photos program, which is new, is free and the resize image feature offers optimal resizing for different purposes (thumbnail, emails or messages, viewing, or custom), It is a very powerful program with many features including editing, 3D features, making slide shows and video editing. Worth a fresh look. Answering. “Which program can I use in a PC (free better) to change the size of pictures, without losing quality? Is it to create a PDF from pictures and make the file lighter?”
Can I have the program for Windows, OSX or Linux?” “Will my pictures stay the same, if I use different programs (PDF, PNG, JPEG, GIF, etc)?” “Is there a good program for Windows, OSX and Linux?” “How to view pictures?” “What about making slide shows?” “How to delete pictures?” “For which picture format?” “What do we do on Windows, OSX or Linux?” “How to open files?” “How to select the picture?” “What is the difference between a JPEG, PNG or GIF?” “Which is the picture format?” “What is the difference between a JPEG, PNG or GIF (JPEG)?” What else is the difference (JPEG, PNG or GIF)?” “What other image format can I view?” “What you see is really what you get?” “How to see the original picture?” “What does a “true” JPEG do?” “What is an image that can be enlarged without losing quality and being saved as a new file?” “Why does that image look so.