Where BMP files come from
BMP is one of the oldest image formats on Windows. You still meet it in places that haven't changed in years: the Paint app on older setups, some scanners and multifunction printers, medical and lab equipment, industrial machines, point-of-sale software and legacy business programs that export reports or charts as bitmaps.
BMP stores pixels with little or no compression, so files are heavy and many websites, email services and phone apps don't accept them. Nobody wants to receive a 20 MB attachment that their phone can't preview. A PDF solves both problems: it opens everywhere and is easy to print, sign or forward.
Typical reasons to convert
A clinic hands you an exam result exported from a device as BMP, and the insurer asks for a PDF. A scanner at the office saves pages as bitmaps, and you need to send them as one document. A legacy program produces a diagram or an invoice as an image, and your accountant wants everything in PDF. In each case you select the files, put them in order and download a single document.
You can mix BMP images with JPG, PNG, WEBP or TIFF files in the same PDF, which helps when your evidence comes from different sources.
Page size, orientation and margins
Choose Letter for the US and Canada and A4 for the UK, India and most other countries. “Same as image” makes each page exactly the size of its picture, with no border, which suits screenshots and diagrams that will only be read on screen.
Orientation can be automatic, portrait or landscape; automatic gives a wide image a landscape page. Margins can be none, small or large. If the document will be printed, a small margin keeps the edges of the image clear of the printer's unprintable area.
On your device, at no cost
The conversion runs in your browser. Your BMP files are never uploaded or stored, so medical images, internal reports and scanned papers stay with you. There's no sign-up, no watermark and no limit on how many files you convert, only the memory of your device for very large batches.
If the resulting PDF is still heavy, open Compress PDF next and pick a level or a target size, without selecting the file again. If you only need a lighter image rather than a document, BMP to JPG or BMP to PNG is the better route.