Most PDF problems aren't random — they're predictable, recurring, and fixable once you know what's causing them. Here are the issues that come up most often, with the fastest path to resolving each one.
1. The PDF Is Too Large to Send by Email
Almost always caused by high-resolution images embedded at full camera or scanner resolution. The fix: run the PDF through WukongPDF's PDF Compression tool at www.wukongpdf.com — medium compression reduces most documents by 50-70% with no visible quality change. If the file is already compressed and still too large, split out the pages you actually need to send, or share via a cloud storage link instead of an attachment.
2. Can't Select or Copy Text
Two possible causes. If clicking on the page selects it as a single image block, it's a scanned PDF with no text layer — run it through an OCR PDF tool to add searchable text. If the cursor moves through words but copy-paste produces nothing, the document has permissions restrictions blocking text extraction — try a different PDF viewer, which may not enforce those restrictions, or contact the document owner for an unrestricted version.
3. The PDF Won't Open
First, try a different PDF viewer — Adobe Reader, Chrome, Preview on Mac. A file that fails in one viewer often opens in another. Check the file size: if it's a few KB when it should be megabytes, the download was incomplete — re-download from the source. If the file is the right size but won't open anywhere, it may be corrupted — run it through a repair tool or request a fresh copy from the sender.
4. The PDF Looks Different on Another Computer
Almost always a font issue. If fonts aren't embedded in the PDF, viewers substitute the closest available font — changing spacing, line breaks, and sometimes the entire layout. The fix is to re-export from the source document with font embedding enabled. In Word's PDF export dialog, this is the default behavior when using File > Save As > PDF rather than Print > Save as PDF.
5. The PDF Prints Blurry
The images in the PDF were embedded at screen resolution (72-96 DPI) rather than print resolution (300 DPI). Screen resolution looks fine on a monitor but blurry on paper. Fix: go back to the source document, replace low-resolution images with higher-resolution versions, and re-export. If the source isn't available, there's no way to recover detail that wasn't in the file to begin with — only higher-quality source images will produce a sharper print.
6. Blank Pages Appearing in the PDF
Usually caused by formatting artifacts in the source document — an extra paragraph mark after a section break, a manual page break followed by nothing, or a section break that forces a new page. Fix: open the source document, turn on formatting marks display (Ctrl+Shift+8 in Word), find and delete the extra mark causing the blank page, then re-export. If you only have the PDF, delete the blank pages directly using a page management tool.
7. The PDF Won't Upload to a Portal
Most common causes: file too large (compress it), PDF version too new for the portal's validator (re-export at a lower compatibility setting), or the file is password protected (remove protection before uploading). If none of these apply, try a different browser — some upload interfaces have browser-specific issues. As a last resort, re-export a fresh PDF from the source document, which often resolves obscure structural validation failures.
8. Links in the PDF Don't Work
Hyperlinks in PDFs are lost when the document is exported using Print to PDF rather than the application's native export function. Fix: re-export from Word or the source application using File > Save As > PDF, not via the print dialog. This preserves links as clickable PDF annotations. If the PDF was already sent and the links need to work, add them manually in Adobe Acrobat or a PDF editor.
9. The PDF Is Slow to Open
Large embedded images are the most common cause — compressing the PDF significantly reduces load time for image-heavy documents. Other causes include complex transparency effects (flatten the document), non-linearized structure (enable Fast Web View in Acrobat), or simply opening the file in a slow viewer. Try Adobe Reader if the browser viewer is slow — it renders most PDFs faster for large or complex files.
10. The PDF Form Can't Be Filled In
If clicking on form fields does nothing, the PDF may be a flat form — the visual appearance of a form without interactive fields. Use a PDF Editor to add text anywhere on the page using the text tool, positioning it over each blank. If the fields are interactive but locked, the form may have been flattened after being filled, or the creator applied permissions restrictions that prevent input. In either case, contact the form issuer for an editable version.