[kccqzy]

Just compressing PDFs is not informative enough to tell the user what it is doing under the hood. Is it subsetting fonts? That's usually harmless. Is it rasterizing the vector graphics? That's generally not fine by me. Is it downscaling the raster graphics? It's probably fine but would depend on the intended audience of the PDF and the DPI. Is it merely optimizing the compression used for compressing the content stream? That's also fine. Is it using some thresholding to reduce grayscale to black-and-white? That's only fine if the document is scanned. Etc, etc.

I can never trust this kind of "simple tool" that magically reduces file sizes without telling me what it's doing. Personally, I think PDF is too complicated a format to have this kind of simple file-size-reduction tool.

[Someone]

For the average user, I think PDF is too complicated a format to NOT have this kind of simple file-size-reduction tool.

Also (from https://www.adobe.com/acrobat/online/compress-pdf.html), they sell a tool that gives you more control:

”How do I compress a PDF without losing quality?

The Acrobat online PDF compressor balances an optimized file size against the expected quality of images, fonts, and other file content. Just drag and drop a PDF into the PDF compression tool above and let Acrobat reduce the size of your PDF files without compromising quality.

For more refined control of optimization settings, you can try Adobe Acrobat Pro DC for free for seven days. Acrobat Pro DC for the Mac or Windows operating system lets you customize PPI settings for color, grayscale, and monochrome image quality. You can also use PDF editor tools, edit scans with OCR functionality, convert PDFs to Microsoft PowerPoint and other file formats, convert PNGs and other image file formats, organize and rotate PDF pages, split PDFs, and more.”