Help & Troubleshooting

If the file is several dozen MB and the page runs slow, try: (1) Open the file in a lighter browser (Chrome or Edge). (2) Close other tabs to free up RAM. (3) Use a smaller file or first compress it with the Compress PDF tool. (4) As a last resort, split the large file into smaller parts before processing.

Make sure the file has a .pdf extension. If the file is actually a PDF but won't open, it may be corrupted. Try opening it in another program (Adobe Reader, browser). If it works in other programs, report the issue — the file may use non-standard PDF features not yet supported.

All tools run entirely in the browser, so large files may exceed available RAM. Solutions: (1) Use Chrome/Edge — they handle memory better. (2) Close other programs and tabs. (3) Process smaller files. (4) If the issue persists, try updating your browser.

If the file doesn't download automatically after processing: (1) Check if your browser is blocking downloads (icon in the address bar). (2) Click the download button manually if available. (3) Try a different browser. (4) Make sure you have enough disk space.

The tools work in all modern browsers: Chrome, Edge, Firefox, Opera, Safari (versions from the last 2 years). Best performance is in Chrome and Edge. Older browsers (Internet Explorer, old Safari versions) are not supported.

Merging dozens of files or files with many pages may take a moment — everything runs locally in your browser. Time depends on your CPU power and RAM. For very large files (over 100 pages), we recommend processing in batches.

Check how the ranges are written. Examples: “1-5” (pages 1 to 5 in one file), “1,3,5” (three files with one page each), “1-5,8,10-15” (three files). Pages are numbered from 1. “Page by page” saves every page separately; to put chosen pages into one file, use “Split by selection”.

If the PDF contains mostly text (not images), compression may not make a significant difference — text is already highly compressed. Image-based PDFs will compress better. Try a higher compression level. If the file is already optimized, further compression may not be possible.

Margins are entered in the unit you choose (points, millimetres or inches); by default nothing is cut. For an A4 page (595 × 842 pt) try 30 pt on the left and right and 40 pt at the top and bottom. There is no preview, so start with small values and check the result. To crop only some pages, tick them on the thumbnails; with no selection every page is cropped.

The default opacity is 50%: a higher value makes the watermark more visible, a lower one fainter. If the text is too large, reduce the font size; on dark pages choose white. The watermark always runs diagonally, and you can place it at the top, centre or bottom of the page.

Redaction works by covering the selected area with a black rectangle. Make sure the rectangle fully covers the text you want to remove. Redaction is permanent — once saved, this operation cannot be undone. Always keep a copy of the original file before redacting.

If page numbers overlap with document content, try changing the position (top/bottom) or alignment (left/right). You can also reduce the font size. For documents with small margins, choose "Bottom" position with right alignment.

Click existing text to correct it. The new text is written in the font you pick from the list of 12, so it may differ from the document’s original font. The old text is covered by a rectangle in the background colour but stays in the file (it shows up when you copy or search), so remove confidential text with “Redact PDF”. For bigger changes, convert the PDF to Word, edit it there and save it as PDF again.

Some formatting loss during PDF to Word conversion is normal — PDF doesn't store style information like a Word document. Tables, columns and complex layouts may need manual adjustment in Word. The simpler the PDF layout, the better the conversion result.

The default scale is 2, which is 144 DPI. For sharper images, raise the scale to 3 or 4 (216 or 288 DPI) before converting. For pages with text choose PNG, which keeps letters sharp; JPG suits photos better.

PDF to Excel table conversion works best for simple tables. Complex tables with merged cells, colors and custom formatting may need manual adjustment. If data appears in one column instead of a table, try exporting PDF to TXT first, then import to Excel with column splitting.

OCR works best on clear scans. Check: (1) Resolution — scan at 300 DPI. (2) Straight pages — straighten crooked scans before OCR. (3) Handwriting — OCR does not recognise it. (4) Language — pick the document’s language from the list of 33 before you start; the wrong language makes recognition much worse. (5) Decorative fonts — they may be read incorrectly.

URL to PDF fetches the page through our server and keeps only its text. It may fail for pages that require signing in, block automated visitors, build their content with JavaScript or redirect to another address — in that case enter the final address from your browser’s address bar. Pages larger than 100 MB and private network addresses are not fetched. You can also copy the page’s HTML code into “HTML to PDF”, which keeps headings, lists and tables.

This is normal — EPUB is a reflowable format where text adapts to screen size, while PDF has a fixed layout. Images, tables and complex layouts may be shifted. If you need the original layout, stay with PDF. EPUB is better for reading on ebook readers and phones.

Save your password in a safe place! OptimaPDF does not store passwords and cannot recover them. If you forget your password, there is no way to open the file. We recommend: (1) Use passwords you can remember. (2) Save the password in a password manager. (3) Keep a backup of the original file before protecting.

Unlocking requires the correct password. If the password is correct but unlocking doesn't work, the file may use an older or rare encryption type. In that case, try opening the PDF in Adobe Reader, enter the password, then save an unprotected copy — and process that copy further.

Check: (1) Which pages you chose — all, the first, the last or a specific one. (2) That the X/Y coordinates fall inside the page; a quick position such as bottom right avoids this. (3) A drawn signature is blue and as thin as your stroke — if it is hard to see, draw it larger or use a text signature.

The tool only fills interactive AcroForm forms. If the PDF looks like a form but has no fields, it's likely a scan or image — in that case, use the edit tool (add text manually) or OCR to recognize text. Some forms filled in Adobe Reader may not be recognized as AcroForm.

PDF/A conversion is "best-effort" — it doesn't guarantee 100% standard compliance. Issues may occur for files with: (1) embedded fonts without license, (2) advanced forms, (3) multimedia (audio, video). Despite the error, the file may work correctly in most archiving programs.

No. AI Chat, AI Summary and AI Translate work with no key and no sign-up — our server sends the requests to the AI service. Anyone can make up to 15 AI requests a day; when the limit is used up, the page tells you in how many hours you can try again.

Response time depends mainly on the length of the text — summarising or translating a long document takes longer than a chat question — and on how busy the AI service is and on your connection. If you wait very long, try a shorter part, for example after extracting the pages you need.

AI models can make mistakes or "hallucinate" — provide information that sounds plausible but is incorrect. Always verify AI answers against the original document. AI works best for: summarizing, finding specific information and generating overviews. Don't trust AI 100% for important documents.