Common PDF Processing Problems and How to Troubleshoot Them

The file won't load or is "not a valid PDF"

The file is password-protected: Tools that don't decrypt files can't work with protected PDFs. If you're entitled to the file, open it with its password in your usual reader and save an unprotected copy.
It's not really a PDF: A file renamed from .docx or .jpg to .pdf is still a Word document or image. Export it properly as PDF from the original application, or use JPG to PDF for images.
The download was incomplete or the file is damaged: Try opening it in your PDF reader. If it fails there too, download it again or ask the sender to resend it.

Compression gave 0% or a larger file: The PDF was already efficient, or text pages were turned into images. See why some PDFs are hard to compress.
Merged or split files add up to more than the original: Each output file carries its own copy of the fonts and resources it uses. It's expected; each part is still self-contained.
A PDF from a few photos is huge: Photos are embedded at full quality. Crop or resize them first, or compress the result — see the JPG to PDF guide.

The wrong pages were split, deleted or extracted: Tools count pages by position in the file, not the number printed on the page. Use your reader's page counter and try again from the original.
Pages are in the wrong order: In Extract PDF Pages, type the correct sequence (for example 1-4, 6, 5, 7-12) to create a reordered copy.
Pages are sideways or upside down: Use Rotate PDF: 90° turns clockwise, 270° anticlockwise, 180° flips. Rotate only the affected pages with "Selected pages".
Pages are different sizes after merging: Merging keeps each page's original size. Use "fit to page" when printing.

Keep the tab in the foreground — mobile browsers pause background tabs.
Close other heavy tabs and apps to free memory.
Work in smaller pieces: convert a range of pages at a time, or merge in groups.
Use a computer for very large scans. Files over 150 MB are refused, and large files can exceed a phone's memory well before that.

Text is blurry: Something converted the pages to images — Extra compression or PDF to JPG. Use lossless options if text must stay crisp.
Text can't be selected or searched: Either the original was scanned (check here), or an image-based step was used. Keep the original for searching.
Form fields or bookmarks stopped working: Document-level features don't always survive page operations. Fill forms before processing, and keep the original for its bookmarks.

Nothing seems to happen on a phone: check your Files or Downloads app — downloads often save silently.
A ZIP file arrived instead of PDFs: multiple outputs are bundled. Tap or double-click the ZIP to extract it.
Browser blocked multiple downloads: allow downloads for the site when prompted, or use the single ZIP download.

Still stuck? Tell us which tool, browser and device you used, and describe the kind of PDF — please don't send the file unless we ask.