8 Common PDF Problems and How to Fix Them
PDF is one of the most widely used document formats in the world, but working with PDF files is not always smooth. Files can be too large to send, locked with forgotten passwords, impossible to edit, missing pages, or simply refusing to open. Each of these problems has a practical solution — and most can be resolved in seconds without installing any software. This guide covers the eight most common PDF problems and how to fix them.
The PDF file is too large to send by email
Why it happens
PDFs that contain many high-resolution images, embedded fonts, or scanned pages can easily exceed 10–25 MB — the typical attachment size limit of most email services. A single scanned document can be 2–4 MB per page, making even short files difficult to attach.
Solution
Compress the PDF before sending. A compression tool reduces file size by optimizing image data and removing unnecessary internal metadata. Most PDFs can be reduced by 40–80% with no visible change in appearance. If the file is still too large after compression, consider splitting it into smaller sections and sending them in separate emails.
The PDF is password-protected and you need to open or edit it
Why it happens
PDFs are commonly password-protected for security. If you know the password but the file is still asking for it, you may be entering it incorrectly (check for caps lock or special characters). If the file was sent to you and you genuinely own the right to access it, the sender needs to provide the password.
Solution
If you own the document and know the password, you can unlock the PDF to remove the password permanently using an online unlock tool. This produces a version of the file that can be opened without a password for future access. Only unlock files you own or have explicit permission to modify.
You cannot select or copy text from the PDF
Why it happens
There are two reasons text in a PDF cannot be selected. First, the PDF may be an image-based or scanned PDF — each page is a flat image rather than a page containing real text data. Second, the PDF may have copy restrictions applied by its creator. Both situations prevent normal text selection.
Solution
For scanned PDFs, use an OCR (Optical Character Recognition) tool to extract the text. OCR analyses the image and identifies the characters, converting them into selectable text. For PDFs with copy restrictions, unlocking the file (if you have the right to do so) removes those restrictions.
The PDF layout looks wrong when opened on another device
Why it happens
PDF is designed to be consistent across devices, but in practice, rendering differences between PDF viewers, operating systems, and screen sizes can cause minor layout variations. More significant problems occur when the PDF was created with embedded fonts that are not available on the viewing device, or when the PDF was generated from a source document with device-specific formatting.
Solution
Re-generate the PDF from the original source document if possible, ensuring all fonts are embedded. If re-generation is not an option, compressing the PDF often resolves minor rendering issues by optimizing the file's internal structure. For documents that originated as Word or PowerPoint files, re-converting them to PDF using a reliable converter produces a cleaner output.
The PDF has pages in the wrong order
Why it happens
Scanned documents, merged files, and PDFs generated from multiple sources often end up with pages in an incorrect or inconsistent order. This is particularly common when combining documents from different people or reorganizing sections of a report.
Solution
Use a PDF page organizer to reorder the pages. An online tool displays all pages as thumbnails that can be dragged into the correct sequence. Once reordered, save the document and the pages will appear in the new order. This is the cleanest approach and takes only a minute for most documents.
You need to edit a PDF but it is not editable
Why it happens
Standard PDFs are not designed to be edited directly. They are presentation-format files, similar to a printed page. Many users expect to open a PDF and modify the text, but this is not how the format works by default. Some PDF readers offer annotation tools, but for actual content editing, the document needs to be converted.
Solution
Convert the PDF to Word format. This extracts the text, formatting, and layout into an editable .docx file that you can modify in any word processor. After making changes, you can convert the Word file back to PDF. The conversion is best for text-heavy documents; complex layouts with many tables and images may require some adjustment after conversion.
Multiple PDFs need to be combined into a single document
Why it happens
Working with multiple separate PDF files — chapters, appendices, attachments, or separately scanned pages — can make document management inconvenient. Submitting or sharing many individual files also creates confusion for recipients. Merging them into a single PDF is the cleaner solution.
Solution
Use an online PDF merge tool to combine multiple PDF files into one. Upload the files in the order you want them to appear, and the tool produces a single unified PDF. This is particularly useful after scanning multiple documents separately, assembling report sections from different contributors, or consolidating application documents for a submission.
A PDF file appears to be corrupted or damaged
Why it happens
PDF files can become corrupted for several reasons: an interrupted download, a failed file transfer, a storage error, or damage caused by a software issue during creation. A corrupted PDF may fail to open entirely, display garbled content, or load only partially.
Solution
A PDF repair tool can attempt to recover the readable content from a damaged file by reconstructing the internal file structure. Recovery success depends on how severely the file is corrupted. For partially corrupted files, the repair process often restores full access. For files that fail entirely, recovery may restore some pages or content. After repairing, download and open the file to check what was recovered.
Preventing Common PDF Problems
Many PDF problems are avoidable with a few simple habits that take very little extra time.
Compress before sending
Check the file size before attaching a PDF to an email. If it is over 5 MB, compressing it first avoids delivery failures and slow downloads for the recipient.
Keep a copy of passwords in a safe place
If you protect a PDF with a password, store the password in a password manager or a secure note immediately. Forgotten passwords on encrypted PDFs cannot be recovered without the original password.
Verify the PDF after converting
After converting from another format to PDF, always open the resulting file and scroll through it to check that all pages, images, and formatting have rendered correctly before sending.
Download files from reliable connections
Interrupted downloads are a common cause of corrupted PDF files. Avoid downloading large files on unstable connections, and verify the file size after download matches the expected size.
Summary
Most common PDF problems have straightforward, free solutions that require no software installation. Whether your file is too large, locked, missing pages, uneditable, or damaged, an appropriate online tool can resolve the issue in seconds.
The key is matching the problem to the right tool: compress for size, unlock for passwords, OCR for unselectable text, organize for page order, merge for combining files, convert for editing, and repair for corruption. All of these tools are available on ToolifyPDF and work directly in your browser on any device.