The page-size selector offers three output options: A4, Letter, and Fit, which matches the original image size.
A discussion on Adobe's community forum notes that converting a PNG to PDF can change the original pixel dimensions depending on the page settings used. Converting PNG to PDF is changing dimensions. - Adobe Community
PNG To PDFHow PNG To PDF Handles Page Size, Margins, And Orientation
Select the PNG files you want to reformat and add them to the upload area.
Select the page size from the dropdown menu.
Choose orientation.
Set the margin preference before starting the conversion.
Configuring Print Layout Controls
Margin choices map to fixed point values: no margin is 0pt, small margin is 20pt, and big margin is 40pt on every side.
When orientation is set to automatic, the tool compares the image's width and height to choose landscape or portrait.
Review the selected page size against your printer requirements.
Confirm the margin setting matches your design intent.
Verifying Output and Resetting
The start-over control clears the upload area right after download, so another batch of PNG files can go through the same page-size and margin setup without a reload.
Save the reformatted PDF to check the new layout.
Open the file.
Click the start-over button to run another layout conversion.
Continue with Combine Multiple PNG Into One PDF or Convert PNG to Searchable PDF.
Frequently Asked Questions about PNG to PDF Page Size, Margins, and Orientation
How do I set the page size?
Match the page size dropdown to A4, Letter, or Fit based on your printer needs.
Where do I adjust the margins?
Open the margin control and pick No Margin, Small, or Big before converting.
How do I choose the orientation?
Pick Landscape, Portrait, or Automatic from the orientation control before converting.
How do I start a new conversion?
Choose the reset link beneath the download button for a fresh layout pass.