The pdf-to-png tool exposes no quality or compression option; its Ghostscript command always requests full png16m output at a fixed factor.
Choose the large PDF you want to check for output size.
Adobe's community forum discusses how embedding high-resolution PNG images inflates a document's file size, since embedded images are stored uncompressed within the file structure. Illustrator file size extremely large due to embedded high-resolution PNGs | Community
PDF To PNGWhy Are PDF To PNG Files So Large
The pdf-to-png tool packages one PNG file per rendered page into a ZIP archive rather than combining pages together.
Review the downloaded ZIP archive to see the individual PNG files.
Compare the total size of the ZIP against the original PDF file.
Checking the Rendered Output
Open the ZIP file and extract the PNG images to your desktop.
Inspect the PNG files for sharp edges and clear text.
Continue with PDF to PNG without transparency or PDF to PNG fixed resolution.
Frequently Asked Questions about Why Are PDF to PNG Files So Large
How do I get the converted images?
Download the ZIP file from the results screen.
Where do I find the individual pages?
Extract the ZIP archive to access the separate PNG files.
How do I check the image quality?
Open a PNG file in an image viewer to inspect the details.
What should I do if the file is too big?
Review the PDF source to identify pages with high-resolution graphics.