The default location to save downloaded PDFs will be different for every gadget and even browser. Desktop Computer: Windows: C:\\\\Users<Your Username>\\\\Downloads Default download location can be changed using browser settings.   Mac: /Users/<Your Username>/Downloads Default download location can be changed using browser settings.   Mobile devices Android: Files app > Downloads folder

Other Places: Download location can be changed under device-wide settings.   \

iOS (iPhone/iPad):

Files App: Navigate to the Downloads folder in the Files app.

Safari: Downloads of PDFs are often located in the Books app. Other Apps: Whenever you downloaded the PDF using an app, look for its pre-programmed download folder. How to Locate Your Downloaded PDFs

Use Your Device's Search Function: Just type in keywords from the title of the PDF or some of the content of it.

Check Download History in Your Browser: Most browsers have a download history which you can browse to dig up recent files downloaded.

Look in Cloud Storage: It may well be that the PDF has automatically synced if you use cloud storage like Google Drive or Dropbox.

For example, file manager applications assist you in quickly finding the way out for organizing your files in the device.