Adobe Acrobat is a professional PDF converter and editor. It can convert various file types to PDF or convert files from PDF to other formats. For example, you can combine images into a PDF on computer using Acrobat, you may also merge documents, spreadsheets, emails, and other file types into a single PDF with it. One issue of converting or merging pictures to PDF with Acrobat is that it will lower the quality of your source images, JPG, JPEG, PNG, TIFF, BMP. You will see the file size dropped after the conversion. Try to convert high resolution photos to PDF, the file size will be much smaller and the quality degraded. So how can we combine pictures into a PDF without losing quality?
Method 1. Save combined PDF as a portfolio, not as a binder
Run Adobe Acrobat on your PC. Go to File > Create > Combine Files into a Single PDF…. The Combine Files window opens.
Click on Options(Gear icon) at the top center, check the option Save as PDF Portfolio. Go to add files and combine them. From now on, Adobe Acrobat simply take what images you have added and doesn’t modify or compress them.
Method 2. Use lossless compression on the images
Another way to assemble high quality TIFF, PNG, JPEG image files into a PDF without noticeably degrading image quality is to use lossless compression. Go to Edit > Preferences ….> Convert to PDF. You can have a look at the BMP to PDF, PNG to PDF and TIFF to PDF conversion preferences. By default they should be at medium quality (JPEG Quality: Medium). So after the conversion, there’s a reduction of graphic quality. You can set the preferences to use lossless compression, so as to minimize the quality degrades of images when assembling them to PDF files. Select BMP, PNG and TIFF separately. Click Edit Settings…. Change the compression settings to JPEG2000 Quality: Lossless. Save the settings. Then go to combine your image files to PDF again.
Update Apr 2019: removed amzn.