Open the PDF in Adobe Acrobat Pro
Go to File
Select Save as Other
Choose Reduced Size PDF
Save the file
Use Adobe Acrobat Online
Upload the PDF
Select the option to compress or reduce file size
Download the compressed PDF
Use Smallpdf
Open smallpdf.com
Select Compress PDF
Upload the PDF
Download the compressed result
Use iLovePDF
Open ilovepdf.com
Choose Compress PDF
Upload the PDF
Download the compressed file
Use PDF24 Tools
Open pdf24.org
Select Compress PDF
Add the PDF
Choose compression settings if available
Save/download the compressed PDF
Use macOS Preview
Open the PDF in Preview
Select File
Choose Export
Set Quartz Filter to Reduce File Size
Save
Use Windows (Microsoft Print to PDF)
Open the PDF in a compatible viewer
Choose Print
Select Microsoft Print to PDF
Click Print
Save the new PDF with a smaller size
Use command line (Ghostscript)
Run a Ghostscript command to generate a smaller PDF using a PDF preset (e.g., ebook/screen)
Save the output to a new file name