Compress a PDF without pretending nothing was lost
The method is a redraw
People ask for compression “without quality loss.” For a photo scan, that phrase usually means “please make it smaller and also identical.” Those are different goals. NexTool’s PDF compress redraws each page as a JPEG. The slider is a quality control, not a target file size. A page of sharp text can turn soft. A page that was already a photograph may look almost the same at a moderate setting and blotchy at a low one. There is no hidden mode that shrinks the file and keeps every vector letter. If you need the letters untouched, do not compress. Send the original, or split off the heavy photo pages and leave the text pages alone.
Start from the original every time you try a new quality. Compressing an already compressed file stacks JPEG damage. The sample on the tool page is a one-page photo-style scan so you can see the method on something that is supposed to be a picture. Your text-heavy contract is a worse candidate. Zoom to 200 percent or print one page. If a signature or a table border breaks into blocks, raise the quality and export again from the original. The smallest file the slider can make is not the goal. The goal is the smallest file that still lets the reader do the job.
Pictures that are not PDFs
A PNG or JPEG you want to attach to mail is a different tool. Image compress exports a picture, not a PDF page. The image guide covers quality, WebP, and batch ZIP files. Do not run a photo through PDF compress by wrapping it in a one-page PDF unless you actually need a PDF. Each conversion is another chance to soften the picture. Keep the camera original until the message is sent and the recipient can open it. NexTool does not store either version.
One honest pass
Start from the scan you trust, set the slider, and export once from compress. Open the result beside the original. Read the smallest line you will be asked about, and look at a face or a stamp at a large zoom. If the page still does the job, the smaller size is a fair trade. If it does not, raise the quality and export again from the original. Stacking a second compress on the first file makes the blocks worse and rarely makes the file usefully smaller. There is no field for a target number of kilobytes, because the method redraws pages as JPEG and the size is a result, not an order. Text-only PDFs that are already small should be left alone. Image files that are not PDFs belong in image compress. The work stays in the browser either way.
Keep the scan that went in
The smaller file is a new picture of those pages, and you cannot ask the site for the sharp one later. If mail still rejects it, lower the slider once from the original or send a link from a drive you already use, rather than running the redraw a second time on the soft copy. Say which file you sent.