Crop PDF's upload step accepts only one PDF at a time (isMultipleInput is false), applying the entered margins to every page of that one file.
Adobe's Action Wizard documentation explains that a single configured action, including a Crop Pages step, can run against one file or a whole collection of files at once. Adobe Acrobat Pro Action Wizard
Crop PDFCrop Multiple PDF Files at Once
Pick the first file from your batch to start the round of cropping.
Enter the margin values for the top, bottom, left, and right edges.
Save that file's current output now.
Repeat the upload step for each remaining PDF file in the batch.
Managing the Single File Limitation
Select the next PDF file from the local directory.
Confirm the margin settings match the previous file.
Save the output.
Verifying the Cropped Output
Open the downloaded PDF to inspect the page edges.
Compare the visible content against the original document.
Continue with Margins do not fit page or Crop does not erase content.
Frequently Asked Questions about Crop Multiple PDF Files at Once
How do I crop multiple PDF files at once?
Upload each PDF file individually to the crop tool.
Where do I enter the crop margins?
Enter the margin values in the input fields after uploading the file.
How do I save the cropped PDF?
Save each cropped PDF before starting the next file's crop.
How do I keep the batch organized?
Rename each cropped output before moving on to the next file.